Building Permit for a House in Thailand (2026) — Steps, Required Documents and Where to Apply, Made Simple

Anyone about to build a house or building cannot skip obtaining a building permit from the local authority. Many people fear it will be complicated, but in reality the process follows a clear legal sequence. What causes delays is usually not the system itself, but incomplete documents or drawings that do not meet the criteria and are sent back. This article therefore brings together the steps, documents, where to submit, timelines and the criteria for engineer-signed drawings in one place.

5 Steps to a Building Permit, from Preparing Drawings to Receiving the Permit

The overall process is as follows:

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The step people most often get wrong is step 5 — they receive the permit but do not build to the drawings, for example shifting the building so that it violates setbacks, or adding floor area. This counts as unauthorized modification and is also an offense. If the design must change during construction, apply to amend the permit first.

What Documents Do You Need for a Building Permit? (Checklist)

The standard document set submitted with the Kho.1 application is as follows (the number of drawing sets is as specified by each local authority):

• Permit application form (Kho.1): available at the local authority office or downloadable from the authority's website
• Land title documents: copies of the title deed or other title documents at actual size, all pages
• Applicant documents: copies of the national ID card and house registration (for a juristic person, the company registration certificate)
• Letters of consent (as applicable): the landowner's consent if building on someone else's land, and the neighbor's consent when building close to the boundary as defined by law
• Construction drawings: site plan, floor plans for every level, elevations, sections, and structural and MEP drawings as the scope requires
• Structural calculations: for buildings that fall under controlled engineering work, signed by the design engineer
• Professional certification letters: certification letters from the design engineer and/or architect, with copies of their professional licenses (COE license / architect's license)
• Site supervisor's letter of consent: submitted with the application or before construction starts, on the form specified by the local authority

For projects where the foundations are significant, many authorities pay close attention to the source of the soil bearing values in the calculations. Read how a soil investigation report relates to the permit application in the article Soil investigation reports for building permit applications

Where Do You Apply, and How Many Days Does It Take?

Apply to the local official where the plot of land is located — in Bangkok this is the district office; in the provinces it is the municipality or SAO (Subdistrict Administrative Organization) responsible for the area (Pattaya City has its own office). Many areas now also accept applications through the authority's online system.

As for timing, the law requires the local official to review the application and notify the result within 45 days of submission. Where necessary, this can be extended no more than 2 times, by no more than 45 days each. In practice, if the drawings and documents are in order from the start, the result often comes sooner than the maximum period. What really causes delays is being asked to revise the drawings or submit additional documents, which restarts the clock with each round.

Another route is construction notification under Section 39 bis — if the drawings are designed and certified by an architect and engineer of the grade required by law, the building owner can submit a notification with the full document set and start construction once the notification receipt is issued, without waiting for the normal permit review. It suits projects that need to start quickly and have a fully qualified design team.

Which Houses Need an Engineer to Sign the Drawings?

The most common question from people building a house is "Does my house need an engineer's signature?" The answer depends on whether the building falls under controlled engineering work under the Engineer Act. The main criteria commonly met by ordinary buildings are:

• Buildings 3 storeys or higher (or structures whose height meets the legal threshold)
• Buildings with a total floor area over 150 square meters
• Buildings with a center-to-center column spacing (span) of 5 meters or more

If any one of these applies, the structural drawings must be designed, calculated and certified by a civil engineer licensed by the Council of Engineers Thailand, with structural calculations attached to the application. In practice, many 2-storey houses exceed 150 m², so most need engineer-signed drawings. In addition, buildings whose area exceeds the threshold must also have the architectural design done by a licensed architect.

Design and drawing certification costs depend on the size and complexity of the building. See the detailed price structure in the article Structural design fees and engineer signing fees. Robust foundation calculations should be based on actual soil profile data from a soil investigation, especially since the Foundation Ministerial Regulation B.E. 2566 (2023) raised the importance of soil data in foundation design. For an overview of the whole design process, read Guide to RC structural and civil engineering design or see the scope of SPN's civil engineering design services