Thailand's ISSB Rules Are Now Law. The First Reporting Year Starts 1 January 2027.

For years, Thailand gave listed companies room to choose. Since 2022, the SEC has required ESG, human rights and greenhouse gas information in annual reporting, but has let companies pick their framework, from GRI to the TCFD recommendations (ESG Today).

That choice is ending. On 28 October 2026, the SEC announced that listed companies must disclose sustainability-related financial information aligned with IFRS S1 and IFRS S2. The nine regulatory notifications behind the change took effect on 26 October (GRC Report).

The first reports are not due until 2028. But they cover 2027, and 2027 begins in a matter of weeks. For companies in the first wave, the data collected from 1 January is the data that will be disclosed, and assured.

What the SEC has decided

• The standard. Disclosures aligned with IFRS S1 (general sustainability-related financial information) and IFRS S2 (climate), built into revised reporting forms including Form 56-1 One Report and the registration statement (GRC Report).
• Assurance. Greenhouse gas emissions disclosures must be verified by assurance providers under internationally accepted assurance standards (ESG Today).
• Transitional relief. Five reliefs, including no comparative information in the first reporting year, flexibility on the reporting timeframe, use of equivalent GHG calculation standards, and a temporary exemption from Scope 3 emissions (Asia Asset Management).

The obligations arrive in four waves (GRC Report):

• Wave 1: SET50 constituents after the December 2026 index review report 2027 information in 2028.
• Wave 2: SET100 constituents after the December 2027 review report 2028 information in 2029.
• Wave 3: All other SET-listed companies, including new listings, report 2029 information in 2030.
• Wave 4: mai-listed companies, REITs, infrastructure funds and trusts, and property funds report 2030 information in 2031.

What the reliefs ease, and what they do not

The reliefs buy time on breadth. They do not buy time on quality.

Scope 3 can wait for now. Scope 1 and Scope 2 cannot, and they must hold up in front of an independent assurance provider from the first report. Comparatives can be skipped in year one, but year one's figures become year two's comparatives, so they have to be right the first time.

The SEC's announcement does not state how long the Scope 3 relief lasts or what level of assurance applies (GRC Report). Until the notification detail is confirmed, the prudent plan is to build for the stricter reading.

Five things to have in place before the reporting year begins

1. Know which wave you are in. SET50 membership is fixed at the December 2026 review. A company near the boundary should prepare as if it is in, because learning the answer in late December leaves almost no runway.
2. Draw the boundary around the group. Under IFRS S1, sustainability disclosures cover the same reporting entity as the financial statements. Data collected plant by plant, or for part of the group, needs to be redrawn around the consolidated group.
3. Make Scope 1 and 2 assurance-ready from day one. For each emissions source: a named owner, the source documents, the calculation method and emission factors, and a review step. An assurance provider tests the trail, not just the total.
4. Bring the CFO into the room. IFRS S2 asks how climate-related risks and opportunities affect financial position, performance and cash flows, and how they are governed. That is finance and board territory, not an appendix to the One Report.
5. Use the Scope 3 relief to build, not to wait. Identify the material Scope 3 categories now and start supplier data requests early, so the end of the relief is a step forward rather than a scramble.

Disclosure quality now carries more weight

The SEC's rules are not the only shift in Thailand's market. The Stock Exchange of Thailand made 2025 the final year of its own SET ESG Ratings and is moving to FTSE Russell ESG Scores from 2026 (ASEAN Exchanges).

Taken together, the two changes point the same way. What a company publishes, in a recognised international format, is increasingly what regulators, index providers and investors assess.

One region, converging rules

Thailand is not moving alone. Malaysia has already written the ISSB-aligned NSRF into Bursa Malaysia's listing requirements, with the largest Main Market companies reporting from financial year 2025 (read our Bursa Malaysia guide). India's listed companies report under BRSR.

For groups with listings or subsidiaries across these markets, each filing still follows its own rules. What can be shared is the layer underneath: emissions and other data captured once, with its source, owner and method attached, then used for a Thai One Report, a Bursa disclosure and a BRSR filing without being rebuilt each time.

Where to begin

Starting in January means starting with the data systems you already have. The question is how quickly they can produce numbers an assurance provider will accept.

At GovEVA, we work alongside finance, company secretarial and sustainability teams to set the reporting boundary, build an assurance-ready evidence trail for Scope 1 and 2, and connect climate disclosures to the financial story. Our agentic AI platform keeps every number traceable to its source, and our advisors guide the judgement calls along the way. That is what a Sustainability Sherpa does: help you read the terrain before the climb.

Get ready for your first IFRS S2 reporting year. Talk to a GovEVA advisor.

Frequently asked questions

When does ISSB-aligned reporting start in Thailand?
SET50 constituents after the December 2026 review report 2027 information in 2028. SET100 companies follow with 2028 information in 2029, other SET-listed companies with 2029 information in 2030, and mai-listed companies, REITs and infrastructure and property funds with 2030 information in 2031.

Is it mandatory?
Yes. Nine regulatory notifications took effect on 26 October 2026, with obligations applying wave by wave.

Do Thai listed companies need assurance on their emissions?
Yes. Greenhouse gas emissions disclosures must be verified by assurance providers under internationally accepted assurance standards. The SEC's announcement does not specify the level of assurance.

Is Scope 3 required in the first year?
No. Scope 3 emissions are temporarily exempt during the initial implementation period. The announcement does not state how long the exemption lasts.

Where are the disclosures filed?
In the SEC's revised reporting forms, including Form 56-1 One Report and the registration statement.

Sources: SEC Thailand, GRC Report, ESG Today, Asia Asset Management, ASEAN Exchanges.