Thailand Sets ISSB Reporting Rollout, With First Company Reports Due in 2028

Largest Listed Companies Face First Reporting Deadline

Thailand's largest listed companies will begin collecting sustainability information under new reporting requirements in 2027 and submit their first reports in 2028, as the Securities and Exchange Commission (SEC) brings corporate disclosures into line with international standards. Nine related regulatory announcements took effect on 26 October 2026, with requirements expanding to other companies, funds and trusts through 2031.

The first group covers companies included in the SET50 index at its December 2026 review. Companies qualifying through the SET100 index in December 2027 follow a year later. The rollout gives businesses different starting dates according to their listing category, while requiring greenhouse gas emissions information to undergo verification using internationally accepted assurance standards.

For investors, the change promises more consistent information about how climate and other sustainability issues could affect company finances. For businesses, it means preparing records, calculation methods and internal checks before the year in which their first report is due.

The final timetable starts later for the two leading index groups than the SEC's initial proposal. The regulator's November 2024 consultation envisaged SET50 reports in 2027 and SET100 reports in 2028. The announced schedule moves both deadlines back by one year, while retaining 2030 for other Stock Exchange of Thailand companies and 2031 for mai companies and specified funds and trusts.

What IFRS S1 and IFRS S2 Require

The International Sustainability Standards Board (ISSB), part of the IFRS Foundation, published its first two standards on 26 June 2023. IFRS S1 covers sustainability risks and opportunities that could affect a company's prospects. IFRS S2 addresses climate risks and opportunities specifically.

Investors and lenders are the intended readers. A useful disclosure explains how an issue could affect a business, rather than simply listing environmental activities. For example, climate information can help readers understand a company's exposure to disrupted operations, changing energy costs or spending needed to adapt its facilities.

IFRS S1 applies a materiality test: companies report information whose omission, misstatement or concealment could reasonably affect decisions by investors, lenders and other creditors. In simple terms, the focus is on information that matters to people deciding whether to provide money to the business.

Thailand's proposed approach also matched the reporting group to the financial statements. A company preparing consolidated accounts, which combine a parent and its subsidiaries, would prepare sustainability disclosures for that same group. This gives readers a consistent view of the businesses covered by the financial and sustainability information.

Reporting Already Exists, but the Framework Changes

Thai companies listed on SET and mai have had sustainability disclosure obligations since 2022. Their annual reports already cover environmental, social and governance information, including human rights and greenhouse gas emissions.

Companies have been able to use different frameworks, including the Global Reporting Initiative Standards and the recommendations of the Task Force on Climate-related Financial Disclosures. Moving toward ISSB standards is intended to make information more internationally comparable, so investors can assess companies using a more consistent set of requirements.

The SEC's November 2024 consultation set out a gradual approach based on company readiness and transition assistance. It also said existing requirements for other sustainability information, such as social matters, would continue through the current comply or explain mechanism. That mechanism asks companies either to provide the required disclosure or explain their reasons for not doing so.

The practical change is a more structured connection between sustainability and financial reporting. Companies already publishing environmental information will need to check whether their data, reporting boundaries and explanations meet the new requirements.

How the Timetable Developed

The roadmap moved from consultation to implementation over nearly two years. Thailand uses the Buddhist calendar in official documents, so the consultation year 2567 corresponds to 2024, while the announcements dated 2569 correspond to 2026.

• 19 November 2024: The SEC published its proposed ISSB disclosure roadmap.
• 19 December 2024: The public consultation closed.
• 12 June 2025: The IFRS Foundation recorded Thailand's regulatory process as still in progress, with feedback under assessment and another consultation planned.
• 26 October 2026: Nine related regulatory announcements took effect.
• 2027: The first group, qualifying SET50 companies, begins its reporting year under the new requirements.
• 2028 to 2031: Reports become due progressively across the covered groups.

The IFRS Foundation's Thailand jurisdictional snapshot, updated on 12 June 2025, described a proposal rather than completed rules. At that stage, effective dates, coverage and several implementation details remained subject to the SEC's assessment.

The snapshot included a statement from Thailand's SEC explaining the purpose of the proposed roadmap:

Working toward the goal of aligning the Thailand sustainability-related information disclosure requirements with the ISSB Standards, the SEC proposed a roadmap that would require listed entities to start disclosing sustainability information in accordance with the ISSB Standards, with extended transition reliefs suitable for the context and readiness of the Thai ecosystem.

The later rollout keeps that gradual structure, but changes the starting dates for the SET50 and SET100 groups. Companies need to distinguish the year they collect information from the following year, when they submit it.

Which Companies Report and When?

SET50 companies qualifying at the December 2026 index review begin applying the requirements to 2027 information and submit reports in 2028. The next group, companies qualifying through the December 2027 SET100 review, begins with 2028 information and reports in 2029.

All other companies listed on the Stock Exchange of Thailand, including initial public offerings, begin with the 2029 reporting year and submit in 2030. An initial public offering, or IPO, is a company's first sale of shares to public investors.

Companies listed on the Market for Alternative Investment, known as mai, begin with 2030 information and submit reports in 2031. The same schedule covers real estate investment trusts, infrastructure funds, infrastructure trusts and property funds, including relevant IPOs.

The 2024 proposal explicitly included companies incorporated abroad but listed in Thailand, as well as businesses intending an IPO. It excluded issuers on LiVEx. It also proposed keeping a company's reporting duty in place after subsequent removal from the qualifying SET50 or SET100 index. These details show why a company's legal structure and index history can matter alongside its current listing category.

Five Measures Ease the Transition

The announced rules include five forms of transition assistance: an exemption from comparative information in the first reporting year, priority for climate disclosures, flexibility over reporting time, temporary use of equivalent greenhouse gas calculation standards, and an initial exemption from Scope 3 emissions disclosure.

Comparative information means the previous year's figures shown beside the current year's results. Waiving it in the first year lets a company begin reporting without having to reconstruct a complete earlier dataset.

The November 2024 proposal specified one year of relief for comparative information and five years for each of the other four measures. Its climate priority allowed companies initially to apply IFRS S2 and the climate portions of IFRS S1, before moving to the full range of sustainability risks and opportunities covered by both standards.

The proposal also allowed sustainability disclosures to appear at a different time from the related financial statements during the first five years. Companies using that relief could disclose through the annual 56-1 One Report within three months of the end of their accounting period.

The October 2026 announcement identifies all five measures but does not give their detailed durations or exact filing extensions. Companies therefore need the operative rules and reporting guidance to determine the precise end of each concession under the revised timetable.

Why Scope 3 Emissions Take Longer

Greenhouse gas reporting divides emissions into three categories. Scope 1 covers emissions from sources a company owns or controls, such as fuel burned in its own equipment. Scope 2 covers emissions associated with purchased electricity and other purchased energy.

Scope 3 covers other emissions along the value chain, including relevant activities involving suppliers, transport, customers and the use of products. Collecting that information often requires data from organisations outside the reporting company, making preparation more demanding.

The 2024 proposal allowed companies to omit Scope 3 for their first five reporting years while reporting Scopes 1 and 2. Its example required the SET100 group to report Scopes 1 and 2 from 2028 and all three scopes from 2033. Those dates belonged to the earlier timetable, under which SET100 reporting started a year sooner than in the announced rollout.

The proposal also allowed alternative international emissions measurement standards for five years before requiring the GHG Protocol Corporate Accounting and Reporting Standard (2004). For SET companies outside the two leading index groups, it gave 2035 as the first reporting year requiring that method.

Verification Adds an Outside Check

Greenhouse gas emissions disclosures must be verified by assurance providers using internationally accepted standards. For companies, that adds a practical requirement to preserve the records behind their calculations and arrange an external review.

The consultation required companies to identify their verifier. It allowed verifiers registered with the Thailand Greenhouse Gas Management Organization (TGO), or providers meeting the alternative conditions in its verification provisions. It cited internationally accepted assurance standards, including ISAE, ISSA 5000 and ISO standards.

The IFRS Foundation's June 2025 snapshot described the SEC's proposal as requiring limited assurance of emissions information. Limited assurance involves an outside practitioner carrying out procedures and reporting a conclusion, with a lower level of confidence than reasonable assurance.

Investors would receive both the company's emissions figures and information about the party checking them. Businesses, meanwhile, must make their measurement process traceable, from the underlying activity records through to the published totals.

Preparation Starts Before the First Report

The SEC has prepared a 56-1 One Report-S form and a disclosure handbook to support implementation. Training for the private sector began in 2024, and the regulator plans to continue that work alongside guidance developed with partners in Thailand and abroad.

For the first SET50 group, the immediate task is readiness for the 2027 data collection year. Waiting until the 2028 submission year would leave companies trying to assemble information after the period being measured has ended.

Companies in later groups have more time, but the work reaches beyond drafting an annual report. It includes deciding which operations fall inside the reporting boundary, assigning responsibility for data, choosing permitted calculation methods and arranging emissions verification.

The gradual rollout balances two concrete aims: giving investors more comparable information and allowing companies time to build reliable reporting systems. The first reports in 2028 will mark the beginning of that process, with coverage expanding through 2031 and transition measures shaping how quickly full disclosures follow.

Key Points

• Nine related regulatory announcements took effect on 26 October 2026.
• Qualifying SET50 companies report 2027 information in 2028; the next SET100 group follows in 2029.
• Other SET companies submit their first reports in 2030, followed by mai companies and specified funds and trusts in 2031.
• The requirements align sustainability disclosures with IFRS S1 and IFRS S2.
• Five transition measures ease initial reporting, including relief for comparative information and Scope 3 emissions.
• Greenhouse gas emissions information must undergo verification using internationally accepted assurance standards.