How a green, social, or sustainability-linked bond reaches market, and where a guarantee fits
A working reference on the end-to-end process of issuing a labeled bond, with depth on Thailand. It covers the standards (ICMA, Climate Bonds, ASEAN), the issuance sequence from framework to post-issuance reporting, the players and what each does, where a credit guarantee changes the mechanics, and the current state of Thailand’s regulation, including the transition and amber-bond rules still in consultation.
A labeled bond is an ordinary debt instrument that carries an additional sustainability claim, backed by a framework and, usually, third-party scrutiny. The most important distinction is between use-of-proceeds bonds and KPI or target-linked bonds.
Use-of-proceeds (UoP) bonds. The label attaches to what the money funds. Proceeds are ring-fenced for eligible green or social projects. The issuer’s general creditworthiness is unchanged, and the greenness lives entirely on the asset side.
KPI or target-linked bonds. The label attaches to what the issuer promises to achieve at the entity level. There is no ring-fencing, and proceeds go to general corporate purposes. Instead, the bond’s financial terms depend on whether the issuer hits pre-agreed sustainability targets.
Transition bonds sit across the two. The label signals that proceeds, or in SLB format the targets, support a high-emitting, hard-to-abate issuer’s credible move toward decarbonisation in sectors such as steel, cement, power generation, and shipping. A transition bond can be structured as either use-of-proceeds or SLB. What makes it transition is the sector and the credibility of the decarbonisation pathway, not the structure. ICMA governs transition through a handbook and guidelines rather than a separate principles document.
ICMA is the voluntary global baseline that almost every other standard references.
Climate Bonds Standard (CBI) is a stricter certification regime above ICMA, with a certification mark awarded against sector-specific, science-based eligibility criteria (its Taxonomy) and confirmed by CBI-approved verifiers. ICMA sets the floor and the common language, while CBI is an optional, more rigorous label on top.
ASEAN Green, Social and Sustainability Bond Standards, issued by the ASEAN Capital Markets Forum (ACMF), build on ICMA with regional overlays such as a geographical or economic connection to ASEAN, the exclusion of fossil-fuel power from eligible green projects, and continuous-disclosure expectations. There are now also ASEAN SLB Standards. The ASEAN Standards act as a regional passport, and many guaranteed deals in the region carry the ASEAN label.
In short, green and social bonds are use-of-proceeds, where the label reflects what the proceeds fund and the money is ring-fenced. SLBs are target-linked, with unrestricted proceeds but a coupon that steps up if the issuer misses its KPIs. Transition can be built either way, and what makes it transition is a credible, science-based decarbonisation pathway in a hard-to-abate sector. ICMA sets the principles, CBI offers stricter certification, and the ASEAN Standards layer regional eligibility on top.
The path from decision to redemption runs in three phases. The bond is structured and approved before it reaches the market, sold during issuance, and then reported on for the rest of its life.
GGGI works upstream of the transaction, on the parts of the process that keep first-time and frontier issuers out of the market.
Beyond the issuer and its banks, a labeled bond pulls in a layer of sustainability-credibility providers on top of the usual bond machinery. This section sets out who does what.
Arrangers, lead managers, and bookrunners are the banks that structure the deal, build the order book, price the bond, and place it with investors. On labeled deals, one of them often acts as the sustainability structuring agent and helps shape the framework.
This is the layer specific to labeled bonds. ICMA recognises four kinds of external review, namely a second-party opinion (SPO), verification, certification, and scoring. The SPO is by far the most common.
An SPO is an independent, pre-issuance opinion on the bond’s framework, not its credit. The provider assesses whether the framework aligns with the relevant ICMA Principles and ASEAN Standards across the four pillars (use of proceeds, project evaluation and selection, management of proceeds, and reporting), and how credibly the financed projects contribute to environmental or social goals. For an SLB, it also judges whether the KPIs and targets are genuinely ambitious rather than business-as-usual. Verification is the related, often post-issuance, step that confirms proceeds were allocated as promised or that an SLB target was met. Certification is a pass-or-fail stamp against the Climate Bonds Standard, which requires a CBI-approved verifier.
The main providers:
The dual-hat point. S&P, Moody’s, and Fitch are credit rating agencies, yet all three also provide second-party opinions, S&P and Moody’s inside their ratings entities and Fitch through the separately branded Sustainable Fitch. They can hold both roles because an SPO is not a credit rating. A rating opines on default risk, while an SPO opines on a framework’s sustainability, and the label has no bearing on the credit rating. The firms run the two through separate teams under information barriers and classify the SPO as a non-rating service. The structure is not free of criticism, and supervisors and researchers continue to scrutinise whether commercial ties colour the sustainability opinion, so independence is a fair question to keep in mind.
A rating measures the issuer’s or bond’s creditworthiness, and the green label does not change it unless a guarantee is wrapped around the bond. Globally, S&P, Moody’s, and Fitch rate on the international scale. In the domestic baht market, issuance overwhelmingly carries a national-scale rating from TRIS Rating, the dominant domestic agency in which S&P holds a 49% stake, or from Fitch Ratings (Thailand), whose national-scale ratings carry a “(tha)” suffix. A guaranteed baht bond typically rates at the top of that national scale.
The global providers are used, and DNV in particular dominates the headline deals. DNV gave the second opinion on Thailand’s sovereign SLB and on EGAT’s SLB, and provided the SPO on CIMB Thai’s sustainability bond framework. Sustainalytics opined on the 2020 sovereign framework. The two should not be conflated, since the sovereign used different reviewers for the 2020 framework and the 2024 SLB. Alongside the globals, TRIS Rating launched a domestic green-bond verifier and SPO service in 2022, priced below the international providers to widen access, though the marquee sovereign and state-enterprise deals to date have used DNV and Sustainalytics.
A credit guarantee is a form of credit enhancement. A guarantor stands behind the bond and lends the issuer its own, stronger rating, so a weaker or first-time issuer can borrow at a rating it could never reach alone. The guarantee is what turns an unrated or sub-investment-grade issuer into a top-rated bond.
In ASEAN, the main local-currency bond guarantor is CGIF, the Credit Guarantee and Investment Facility, a multilateral trust fund established in 2010 under the Asian Bond Markets Initiative, sponsored by ASEAN+3 and the ADB and hosted by the ADB. GuarantCo and the ADB itself also provide guarantees and partial credit enhancement in the region. The aim of this work is to deepen local-currency bond markets so companies borrow long and local rather than short and in foreign currency, the maturity and currency mismatch that drove the 1997–98 crisis.
What the guarantee covers. A full guarantee is irrevocable and unconditional and covers 100% of principal and interest for the life of the bond. CGIF’s single-issue size runs up to about USD 140m equivalent, with tenor up to 10 years and extendable to 15 with justification. Partial guarantees, covering a share of the bond or a defined risk, also exist.
How it changes the rating. A guaranteed bond carries the guarantor’s rating, not the issuer’s. CGIF is rated AA by S&P on the international scale. On a national scale, an AA international guarantor maps to the top of the local scale, AAA(tha) in Thailand, so a guaranteed baht bond rates AAA domestically even though the guarantor is AA internationally. The distinction between the international and national scale matters and is often misunderstood. The effect is that a sub-investment-grade, unrated, or first-time issuer prints at the highest domestic rating, with tighter pricing, longer tenor, and access to rating-constrained institutional investors.
Who benefits. Both sides. The issuer gets cheaper, longer money and market access it could not reach alone. Investors get a top-rated instrument and exposure to issuers and sectors otherwise off-limits. For labeled bonds, the guarantee resolves the tension between ESG-mandated investors wanting sustainable assets and being rating-constrained.
The fee. The guarantor charges an annual fee on the guaranteed amount, priced off its assessment of the issuer’s standalone credit risk, tenor, and structure. The issuer’s all-in cost is the low guaranteed coupon plus the fee, and the deal works when that total is below the higher coupon the issuer would pay unguaranteed.
The parallel credit assessment. While the issuer runs its public process, the guarantor runs its own independent credit underwriting alongside it, because it takes the issuer’s full default risk for as long as 15 years. That work covers financial and business-risk analysis, cash-flow and covenant modelling, structuring to protect recovery, an internal credit-committee approval, and, for labeled deals, its own ESG review. The distinction from a rating analyst is fundamental. A rating analyst opines, while the guarantor underwrites and bears the exposure, taking a principal credit position and living with the risk for the life of the bond.
Thailand’s SEC put a dedicated regime for green, social and sustainability (GSS) bonds in place in 2020. Its core requirements are compliance with internationally recognised standards (the ICMA Principles and, in practice, the ASEAN GSS Bond Standards), disclosure before and after offering, and a qualified external independent reviewer to certify or opine. The SEC also offers incentives. It has waived application and filing fees for ESG bonds, waived annual registration fees for longer-dated (over seven-year) sustainable bonds, and waived registration fees for SLBs aligned to the Thailand or ASEAN Taxonomy from 1 June 2025 to 31 May 2028.
The GSS and SLB part of the market is therefore mature and rule-based. What is new, and not yet finalised, is transition finance.
There are two distinct SEC consultations, easy to conflate. The first, around October 2025, proposed enhancements to the existing SLB regime, letting SLBs tie financial-return features (not just coupon step-ups) to KPI achievement, allowing a zero-coupon SLB format, and updating filing forms. The second, around 21 April 2026 with comments to around 11 May 2026, is the main transition-finance consultation. As of 31 May 2026 it is a public consultation, not an effective rule, with the SEC targeting effect in Q3 2026.
What the April 2026 draft proposes:
The Thailand Taxonomy is the classification backbone the new bond rules rest on. Phase 1 (2023) covered energy and transport. Phase 2 (27 May 2025) added agriculture, construction and real estate, manufacturing, and waste. Amber bonds are definable because of the taxonomy, and the SLB fee waivers are conditioned on alignment with the Thailand or ASEAN Taxonomy.
Thailand is among ASEAN’s most developed sustainable bond markets, anchored by both sovereign and corporate issuance. The landmark transaction is the sovereign SLB. The Government of Thailand, through the Public Debt Management Office (PDMO), issued Asia’s first sovereign SLB on 29 November 2024, a THB 30bn (about USD 865m) 15-year bond, oversubscribed 2.8 times. Its KPIs are a 30% cut in total GHG emissions by 2030 against business-as-usual, and annual zero-emission-vehicle registrations of 440,000 by 2030. It was the third sovereign SLB globally and the first in Asia. The PDMO’s Karas Boonruang has been the Thai SLB voice on 2025 Asia panels.
Among corporates and state enterprises, EGAT issued a maiden sustainability-linked bond and CIMB Thai issued the first subordinated green bond in Thailand. The outstanding market size is unverified and should not be cited as a hard figure.
How does a green bond differ from an SLB? A green bond is use-of-proceeds, ring-fenced for eligible green projects, with the label depending on what is funded. An SLB is target-linked, with unrestricted proceeds but a coupon that steps up if the issuer misses its KPIs. A green bond rewards an asset, while an SLB rewards a company-wide trajectory. SLBs suit transition-sector issuers that want flexibility but accept entity-level targets.
What is an SPO, and can a rating agency provide one? A second-party opinion is an independent assessment of a bond’s framework, not its credit. It tests alignment with the ICMA Principles and, for an SLB, the ambition of the targets. S&P, Moody’s, and Fitch all provide SPOs (Fitch through Sustainable Fitch), alongside specialists such as Sustainalytics, DNV, and ISS-Corporate. A rating agency can provide both because an SPO is not a credit rating, and the firms run the two through separate teams under information barriers.
How does a credit guarantee change a transaction? A guarantor wraps the bond with an irrevocable, unconditional guarantee of principal and interest, so the bond carries the guarantor’s rating rather than the issuer’s. A first-time or sub-investment-grade issuer then prints at the top domestic rating, with tighter pricing, longer tenor, and access to rating-constrained and ESG-mandated investors. The guarantor underwrites the issuer’s full default risk independently, structures for recovery, and approves through its own credit committee, because it owns the risk.
How can a bond be AAA if its guarantor is rated AA? Two scales. AA is an international rating. National-scale ratings re-anchor to the strongest credits within a country, so an AA international guarantor sits at the top of the local scale, AAA(tha) in Thailand. Domestic investors and their mandates reference the national scale.
What is the status of transition finance regulation in Thailand? Still at consultation, not yet an effective rule. The SEC ran a public hearing on transition and amber bonds in April and May 2026 and is targeting effect in Q3 2026. A separate, earlier consultation in late 2025 enhanced the existing SLB rules. The green, social and sustainability and SLB regime has been in force since 2020. Transition and amber bonds build on the Thailand Taxonomy’s traffic-light system, with amber bonds financing taxonomy-amber activities such as gas-fired power within emissions thresholds.
What is the Thailand Taxonomy and why does it matter for bonds? A national classification of economic activities by climate alignment, sorted into green, amber, and red. Phase 1 (2023) covered energy and transport, and Phase 2 (27 May 2025) added agriculture, construction and real estate, manufacturing, and waste. It matters because the new transition and amber-bond rules and the SLB fee waivers all rest on it, making it the definitional backbone for transitional finance and a tool against greenwashing.
What is the greenwashing risk, and how is it managed? For use-of-proceeds bonds, the risk is proceeds drifting to ineligible uses or overstated impact, managed through ring-fencing, an SPO, and allocation and impact reporting. For SLBs, the risk is unambitious or immaterial targets and weak step-ups, managed through SPO scrutiny and mandatory verification. For transition bonds, the risk is transition-washing, managed through a credible, science-based transition plan and taxonomy anchoring. A guarantor also carries reputational risk and runs its own ESG review before wrapping.