Thai Environmental Impact Assessment (EIA) Process

TL;DR

Environmental Impact Assessment (EIA) in Thailand is required for project types listed in MoNRE Notifications under the Enhancement and Conservation of National Environmental Quality Act B.E. 2535 (1992). Environmental + Health Impact Assessment (EHIA) applies to a sub-set of projects with serious health implications. Timelines: 6-18 months for EIA, 12-24 months for EHIA.

Project Categories

• Industrial estates and factories above size thresholds.
• Mining, quarrying.
• Petroleum.
• Power generation (above 10 MW for fossil).
• Dams, irrigation.
• Ports, airports.
• Hotels with 80+ rooms.
• Real-estate projects above 80 rai.
• Hospitals 30+ beds.

Process Steps

1. Screening (does project trigger EIA / EHIA list).
2. Scoping.
3. Baseline studies + impact prediction.
4. Mitigation measures + monitoring plan.
5. Public consultation (1-3 rounds depending on EIA vs EHIA).
6. ONEP (Office of Natural Resources and Environmental Policy and Planning) review.
7. Expert Committee deliberation.
8. Approval recorded; conditions attached.

EHIA Additional Layers

• Health Impact Assessment study by recognised consultant.
• Public consultation reach broader.
• Independent Organization review (Section 67 framework).

Common Mistakes

• Late discovery that project triggers EIA — restart at concept.
• Insufficient public-consultation reach.
• Skipping baseline season variability.
• Approving construction-design before EIA approval.

FAQs

1. Foreign-invested project considerations?

Same EIA rules; BOI promotion does not waive EIA.

When an EIA Is Required

Environmental assessment is required under the Enhancement and Conservation of National Environmental Quality Act B.E. 2535 (1992), as amended by the further Act of B.E. 2561 (2018). The Ministry of Natural Resources and Environment issues notifications listing the project types and sizes that must obtain an EIA before the relevant permit or licence can be granted — typically large infrastructure, industrial estates, mining, power plants, dams, large hotels and condominiums, and similar developments. The most sensitive categories that may seriously affect communities, natural resources or health require the more rigorous Environmental and Health Impact Assessment (EHIA), which includes enhanced public participation.

The Approval Path

A licensed consultant prepares the report, which is reviewed by the Office of Natural Resources and Environmental Policy and Planning (ONEP) and considered by an expert review committee; approval (often with conditions) is a prerequisite for the construction or operating permit. Meaningful public consultation is a core requirement, and baseline data should reflect seasonal variability. A frequent and costly mistake is finalising construction design or starting works before EIA approval — permits obtained without a required EIA are vulnerable to challenge, and the Administrative Court has cancelled approvals granted in breach of the process. BOI promotion does not waive the EIA obligation.

2. How long does an EIA take?

It varies widely with project complexity and the quality of the report, but from scoping and baseline studies through committee review it commonly runs several months to over a year, so it should be built into the project timeline early.

Related Reading

• Business in Thailand Hub
• Environmental Law Hub
• Environmental Offences