Building Permit in Thailand: SAO Documents and Timeline

A Building Permit in Thailand Starts With the Khor. 1 Form

Applying for a building permit in Thailand begins with a single sheet of paper known as the Khor. 1, the application form prescribed under the Building Control Act. That one page has to state who is applying, which land parcel the work is on, how many storeys the building has and how much usable floor area it contains. If any of those details fail to match the construction drawings attached to it, the file is handed straight back to you at the counter.

Land outside municipal boundaries in Korat (Nakhon Ratchasima), Roi Et, and the Pak Chong and Khao Yai areas is mostly administered by a Subdistrict Administrative Organization (SAO, or Or Bor Tor). That means you file at the SAO where the land is located, not where you happen to be registered as a resident. If the parcel straddles two subdistricts, call the engineering division and confirm before you make the trip.

The applicant can be the landowner, a relative, or a home-building company acting under a power of attorney, but the permit is issued in the applicant’s name, never the contractor’s. That distinction matters later, when you apply for a house registration number and for permanent electricity and water meters. Foreign nationals generally cannot own land in Thailand, so an expat building here is usually doing so on land held by a Thai spouse, a Thai company or under a long lease, and the permit paperwork has to follow whoever actually holds the chanote (title deed).

Documents to Prepare Alongside the Application

The core bundle is a copy of every page of the chanote with a certification signature on each sheet, copies of the applicant’s ID card or passport and house registration, and the construction drawings together with the structural calculations. The number of sets required varies from one local office to the next, but three to five is typical. Ask before you print, so you only pay the drawing shop once.

If the applicant is not the landowner, you also need a written consent letter allowing construction on that land, with copies of the landowner’s ID card and house registration attached. Where the title deed carries several names, every single co-owner has to consent, and where the registered owner has died, the inheritance has to be settled first. In practice this is the point at which applications sit unresolved the longest.

You must also attach copies of the professional licences of the architect and the engineer who signed the drawings, together with their letters confirming that they act as the designer and the site supervisor. Some SAOs additionally ask for a sketch map showing the location, photographs of the site as it stands today, and a letter of consent from the neighbouring landowner.

Drawings and Professional Signatures

The drawings you submit have to cover both the architecture and the structural engineering: a site plan showing the setbacks, floor plans for every level, elevations, sections, the foundation layout, the column and beam layout, reinforcement details, and the building services in whatever detail the local office requires. A handsome set of plans and elevations on its own is not enough to file.

Thai law requires certain categories and sizes of building to be designed and supervised by a licensed professional, and an ordinary two-storey house falls squarely inside that requirement. The drawings therefore need original signatures from an architect and an engineer, each with their licence number. Photocopying the plans of somebody else’s house and filing them does not work.

The structural calculations are the document homeowners most often overlook, yet they are exactly what the engineering division actually opens and reads, because they have to correspond to the soil conditions of that particular plot. Many parts of Isan have soft soil layers that call for a foundation design quite different from a house in town. A soil investigation before the drawings are produced therefore helps twice over: once for safety, and once for getting the permit through.

How Long Does a Building Permit Take? What the Law Says

The Building Control Act requires the local authority to review the application and notify the applicant of the outcome within 45 days of receiving a complete and correct submission. If the review cannot be finished in that window, the deadline can be extended by up to 45 days at a time, for a maximum of two extensions, and the applicant must be notified in writing before the existing deadline runs out.

In practice, for a straightforward house with complete paperwork and drawings that raise no compliance issues, many SAOs issue the permit considerably faster than that. Even so, it is unwise to build your programme around the best-case outcome. Bear in mind too that the clock starts on the day the office formally accepts your application, and any period during which the file has been sent back to you for correction does not count.

What comes out at the end of the review is the building permit itself, known as the Or. 1, and it is valid for one year from the date of issue. If the house is not finished within that year, you can apply to renew the permit, but the application has to be made before it lapses. Start that about a month ahead rather than waiting until it has already expired and then asking what to do.

The Section 39 bis Alternative, and the Fees

Alongside the standard route, the law offers an alternative under Section 39 bis of the Building Control Act. Instead of requesting a permit, you notify the local authority, submitting the drawings, the structural calculations and the names of the licensed professionals who certify that the design and the construction will comply with the law. Once you hold the acknowledgement of that notification, work can begin without waiting for a review decision.

This route suits projects with a full professional team and genuine confidence in the design, because liability rests directly with the professionals who signed the certification. If an inspection later finds that the construction departs from what was notified, the authority can order corrections or stop the work altogether. Homeowners who are not in a particular hurry therefore tend to prefer the ordinary permit route.

As for the permit fee and the plan-checking fee, both are calculated per square metre of building area, and they amount to a very small sum next to the cost of the house itself. The rates are set by ministerial regulation and the details can differ slightly between local authorities, so for the practice actually applied in 2026, ask the engineering division directly rather than relying on a figure that has been passed around second-hand.

How to Get Your Permit Approved on the First Attempt

The most common cause of delay is setbacks and open space: the distance from the boundary, the setback from a public road, and the required ratio of open ground to building area. A house placed too close to a boundary, or one with openings facing a neighbouring plot at a distance the law does not permit, has to go back to the designer and be resubmitted.

The second most common cause is missing signatures and paperwork, such as no landowner consent letter or a drawing sheet the designer forgot to sign. The third is the comprehensive town plan, because each land-use colour carries its own rules on building type and density, and the Pak Chong and Khao Yai areas have specific restrictions that need checking before the design work starts, not after.

The most effective single step is to go and talk to the engineering division with a copy of the title deed and a rough sketch before you commission the real drawings. It takes less than half a morning, and you come away knowing which zone the plot falls in and what extra documents this particular office likes to see. Home-building companies such as OBILIS normally include document preparation and permit filing within their scope of work from the outset. Handling it yourself is entirely doable, but budget for several trips back and forth to the SAO office.

To get a rough budget before you talk to anyone, try our house price calculator, or contact the OBILIS team to talk through your plot.

Related reading: Temporary Electricity and Water for Construction in Thailand and Construction Contracts in Thailand: 7 Clauses to Read First

Frequently Asked Questions

What happens if I build without a permit?

The local authority has the power to order the work stopped, to order corrections, and to order demolition where the building cannot be brought into compliance, and there are penalties under the Act. Beyond that, the knock-on problems run on for years: obtaining a house registration number, getting permanent utility meters connected, and selling or mortgaging the property later all become difficult.

My Or. 1 permit expired before the house was finished. What now?

File a renewal application at the same SAO before the expiry date, together with documentation showing how far the work has progressed. Renewals are generally granted a year at a time. If you let the permit lapse entirely, you may have to submit a completely fresh application.

Can I use a free government house plan for the permit application?

Yes, provided the set you are using carries the certifying signatures of an architect and an engineer. Have an engineer review the foundation design against the actual soil conditions of your plot first, though, because standard plans are drawn on general soil assumptions that may not match the land you have bought.