Thailand’s ISSB-aligned disclosure roadmap pairs Scope 1 and Scope 2 emissions with assurance from the beginning of the climate-first rollout. That makes data quality and provider readiness central to implementation.
ISSA 5000 is the likely international baseline to watch, but it should not be described as Thailand’s final mandatory standard yet. The IAASB listed Thai adoption as in progress in May 2026, and the Thai SEC’s November 2025 policy announcement referred more broadly to assurance performed under internationally accepted standards.
What the Thai SEC has decided
The SEC maintained its direction to align listed-company sustainability disclosures with IFRS S1 and IFRS S2, beginning with climate information. The initial phase focuses on Scope 1 and Scope 2 greenhouse gas emissions accompanied by standardized and reliable assurance.
Eligible providers may include verifiers registered with the Thailand Greenhouse Gas Management Organization or other verifiers using internationally accepted assurance standards. The SEC was still amending regulations and related documents after revising the scope and timetable in November 2025.
Our Thailand ISSB roadmap guide explains the phased disclosure direction and the need to confirm final implementing amendments.
The open points matter. Final rules should determine the reporting cohort dates, accepted assurance standards, provider qualifications, assurance level, covered emissions, and transition reliefs.
Where ISSA 5000 can fit
ISSA 5000 can be used over sustainability information prepared under any suitable criteria, including ISSB-aligned disclosures and greenhouse gas reporting criteria. It supports both limited and reasonable assurance and is designed for accountants and other assurance practitioners that meet the relevant quality, ethics, and independence conditions.
If Thailand adopts the standard or a local equivalent, it can create a consistent engagement framework across provider types. Thai subsidiaries may also encounter ISSA 5000 through an overseas parent’s group assurance instructions before domestic adoption is complete.
Build assurance into Scope 1 and Scope 2 reporting
Start by proving completeness. Maintain a controlled list of group entities, facilities, meters, energy accounts, fleet assets, fuels, process sources, and refrigerants. Reconcile the list to finance, asset, property, procurement, and operational records.
For each emissions source, retain:
- Original source evidence and the reporting period it covers.
- Units, conversions, and treatment of missing data.
- The emission factor source, version, geography, and approval.
- The calculation method and any manual adjustment.
- Preparer and reviewer evidence, including resolved exceptions.
Document the organizational boundary and consolidation approach. If a reporting entity uses operational control, explain how leased sites, joint arrangements, franchises, and outsourced operations are treated.
Align different provider models
Thailand’s proposed provider pathway may involve accounting firms and technical verification bodies. Management should require a clear engagement standard, ethical and independence basis, quality management framework, and statement of the information and assurance level covered.
Ask how the provider will use engineers, climate specialists, IT professionals, or component practitioners. Specialist competence does not replace overall engagement quality and accountability.
Before appointment, simulate a request list over a representative facility and a group-level consolidation. Trace a sample from the reported total to source and select source records to confirm they were included. Correct system-level issues before expanding the process across the group.
Keep the disclosure and assurance timelines connected
The sustainability, finance, risk, internal audit, and operations teams need a single close calendar. Set source-data cut-offs, review deadlines, evidence freeze dates, and escalation routes that allow assurance issues to be resolved before the annual filing.
Carbon Impact’s ISSA 5000 assurance-readiness workflow helps Thai listed companies connect ISSB-aligned disclosures to source data, calculation history, evidence, controls, and group owners.
This article reflects information available on August 10, 2026. Thailand’s implementing rules and ISSA 5000 adoption are still developing. This is general information, not assurance or legal advice.
Sources
See how Carbon Impact supports ISSA 5000 reporting — from data collection to disclosure.