How to verify a building permit in Thailand
Legal due diligence
A buyer's most expensive mistake in Thailand is trusting a slick PDF. A building permit is easy to fake at a glance, and in 2026 that has already happened on Samui. Let's break down which document you actually need and how to verify it — calmly and step by step.
On Samui, authorities investigated forged permits that looked like official Or.1 / อ.1 documents but were never registered in the municipal system and carried forged signatures. There is only one defence: don't "check the paper by eye" — confirm the number and the case file with the body that issued it.
01The bottom line
The core authorising document for a villa, condominium, resort or any building is the ใบอนุญาตก่อสร้างอาคาร (Building Construction Permit). On the official forms it is called แบบ อ.1 and rests on Section 21 of the Building Control Act B.E. 2522 (1979).
There is a separate fast-track route under Section 39 bis — but it is not the same document: it uses a notification and the ยผ. series of forms. And an EIA/IEE, a hotel licence, condo registration and a land subdivision approval are entirely different legal regimes. None of them replaces the building permit.
That's why you can't rely on a developer's PDF, a brochure or an agent's word alone. Cross-check at least four blocks: the permit itself (อ.1 or 39 bis documents), the approved plans, the land title and plot boundaries, and the sector-specific approvals — if the project is sold as a condo, resort, hotel or housing estate.
02Which document you actually need
An อ.1 permit must contain at least: the permit number, the building owner's name and address, the construction site, the land title details (โฉนด / น.ส.3 / ส.ค.1), the type, number, intended use and floor area of the buildings, parking and access roads, the date of issue, the validity period and the signature of the local authorised official. On the reverse — renewal stamps.
The term is not open-ended. For buildings under 10,000 m², the permit is usually issued for one year, and a renewal is processed separately — and must be visible either on the reverse or as a separate record from the authority.
So what are "39 bis" and "BP1"?
39 bis is construction by notification, with a full set of professionally certified documents; it uses the ยผ.1 and ยผ.4 forms. If a developer shows a ยผ. series document or says "39 bis approval", that's a different route — not an ordinary อ.1 permit.
As for "BP1", it is not confirmed as a permit name in official Thai sources. If a sale mentions "BP1", insist on clarification: is it actually อ.1, is it a 39 bis notification, or is it simply the seller's internal commercial label?
03What does NOT replace the permit
This is where buyers are most often confused: one document is shown and "all permits are in place" is claimed. Each of these covers only its own subject.
| Document | What it confirms | What it does NOT confirm |
|---|---|---|
| แบบ อ.1 building permit | the right to build a specific building on a specific plot per the approved plans | hotel operations, condo registration, EIA, subdivision |
| IEE / EIA / EHIA environment | environmental clearance where required; status is checked in Smart EIA | does not replace the building permit |
| Hotel License hotel | the right to run a hotel operation (via DOPA) | that the building itself was built lawfully to that design |
| Condo Registration condo | that the building is registered as a condominium; without this, unit titles cannot be transferred properly | does not replace the construction permit |
| Subdivision estate | that the land subdivision is approved and on record with the Land Department | the legality of a specific building and the right to start building |
04Who issues it and where the records are kept
The permit is issued by the local authorised body (เจ้าพนักงานท้องถิ่น): the municipal mayor, the head of a subdistrict (OrBorTor), the head of a Provincial Administrative Organisation (PAO) or the Governor of Bangkok. The central DPT department sets policy and standards, but you must look for the permit primarily with the local body that handled the case.
Hence a key point: the original record is held not in some "general Thai property registry" but in the specific local body. That's why verification is almost always multi-channel.
05How to verify authenticity and match to the project
Request the full file, not a single sheet
A real check needs not "one pretty PDF" but a package: a certified copy of the อ.1 (or the set of ยผ.1 / ยผ.4 forms for 39 bis), all approved plans with stamps and signatures, a copy of the chanote from both sides, documents proving the developer's right to the plot, the landowner's consent (if the permit holder and the landowner are different parties), the architect's and engineer's certificates, and — for a condo / resort / estate — the relevant sector approvals. For multi-plot projects, demand a plan with all chanote numbers.
Cross-check the permit itself
These must match: the permit holder's name, the construction site, the land title number, the building's description and floor area, the date of issue, the validity period and the signature of the local authorised official. The number looks like เลขที่ … / พ.ศ. … — a local sequential number and year; there is no single nationwide format, and numbering is kept locally.
Match the project to the permit
If the website is selling, say, 12 villas of 280 m² each, but the permit and plans show different buildings, a different use or a smaller area, that's a red flag. The law (Section 31) prohibits building in deviation from the approved plans without separate processing.
Check the plot, not a "similar" one
Take the chanote number from the permit or plan → cross-check it against the title copy from the Land Office → make sure the layout shows exactly the parcel being sold to you, including adjoining lots. When buying via leasehold, also check the registered lease and the landowner's consent to construction.
A foreigner can be the applicant for a permit where there are grounds or the landowner's consent. A permit in the name of a company, a Thai owner or a lessee does not in itself make the document invalid — what matters is that the chain of rights to the plot is documented.
Has it been altered, has it expired?
Check three classes of documents: renewal stamps (the fields exist in อ.1), additional permits and amended plans, and violation orders — the ค. series of orders (for example ค.3 — a stop-work order, ค.4 — a prohibition on use). If the developer doesn't show them, it doesn't mean they don't exist; it means they have to be requested from the local body.
06Registries and Koh Samui specifics
Thailand has no single nationwide public system where you can instantly verify every building permit in the country by number. There are local services for filing and tracking status (BMA OSS for Bangkok, the government BizPortal) — but these are not a registry for third-party verification.
For the adjacent approvals, though, the public trail is better: environment — Smart EIA Plus, subdivision and condo — a Land Department search, hotels — DOPA services. And if the local body offers no online building-permit search, the Official Information Act gives you the right to request a copy or a certified copy from the state agency.
On Samui, the building permit is sought primarily at the Koh Samui municipality (its public works department is linked to the 2026 forgery investigation). The land side — through the Surat Thani Land Office, Koh Samui branch. The environment — ONEP / Smart EIA. And keep additional restrictions in mind: the island has environmental and zoning rules, including coastal setback zones, and town-plan compliance is checked before the permit is even issued.
Partly — yes. On your own: EIA status via Smart EIA, the presence of a subdivision / condo in the Land Department databases, the hotel side via DOPA, and a request for a copy from the municipality under the Information Act. But a full and reliable check of the building permit itself on Samui usually requires direct contact with the municipality — often in Thai and frequently in person or by written request.
07Checklist before the reservation payment
A calm order of operations before paying the reservation fee:
- Request the package, not a sheet. อ.1 or the 39 bis set, the approved plans, the chanote, company documents, the landowner's consent, the architect's and engineer's certificates, plus the sector approvals for the project type.
- Cross-check the title numbers. The permit must list the exact chanote on which the project stands — all of them, if there are several plots.
- Check the term and renewals. If the term has expired, request the renewal page or a separate decision from the authority.
- Match the project to the plans. The number of units, the number of floors, the area and the use from the marketing — against the approved plans. Any material discrepancy is a reason to stop.
- For a condo — check the condominium regime, not just the building permit. "It'll be a condo later" without a clear registration roadmap is a high risk.
- For a resort / "guaranteed yield" — separately check the hotel regime. A building permit ≠ a hotel licence.
- Check the EIA/IEE. For large buildings and complexes, status can be looked up in Smart EIA.
- On Samui — send a separate request to the municipality: to confirm the permit number, owner, plot, plans and the presence of any orders or amendments. A certified copy where possible.
- A copy of the อ.1 or the 39 bis package + all approved plans with stamps.
- A copy of the chanote from both sides and confirmation of the developer's authority.
- The landowner's consent — where applicable.
- EIA/IEE status; for an estate — subdivision; for a condo — registration; for a resort — the hotel regime.
- External confirmation from the municipality, the Land Office and, where needed, ONEP / DOPA.
08Risk matrix and fraud schemes
| Situation | Risk | Rating |
|---|---|---|
| Only an EIA is shown, but no อ.1 / 39 bis | environment is in place, but not the right to build the building | High |
| A hotel licence is shown instead of a building permit | a hotel ≠ the legality of the construction | High |
| The chanote number in the permit doesn't match the plot | swapped project or plot | High |
| More units/area advertised than in the plans | selling an unapproved volume | High |
| The permit has expired, no renewal shown | building without a valid permit | High |
| The Samui municipality doesn't confirm the number | forgery or a "ghost permit" | Critical |
The most common schemes in brief: a forged permit that looks like the real thing (defence — confirm the case file with the authority); a document swap — an EIA, hotel or condo paper presented as "all permits"; a configuration that doesn't match the plans — more units or a different area; and off-plan before the land is checked — a "villa in an estate" with no subdivision, or a "condo unit" with no condo registration.
Put plainly: on Samui a buyer can verify a great deal themselves — but you shouldn't pay a reservation fee until you've seen not a marketing "permit" but the linked set of documents and external confirmation from the municipality, the Land Office and, where needed, ONEP / DOPA.