News & Promotion

Thailand home-construction contracts: check the documents before work begins

For an expat, retiree or cross-cultural family planning a custom home in Chiang Mai or Lamphun, the drawings and quotation are only part of the project record. A home construction contract in Thailand must also identify the work, price, schedule and responsibilities in terms that both sides can verify.

On 10–11 May 2026, Thailand’s Office of the Consumer Protection Board (OCPB) published information about home-construction disputes and restated key points from the 2016 controlled-contract rules for businesses hired to construct an entirely new residential building. This was a 2026 reminder about existing rules, not a new law introduced in 2026.

Drawings and the construction BOQ serve different purposes

OCPB’s explanation says that the agreement for a new residential building should be accompanied by plans and a bill of quantities and prices, commonly called a BOQ. The drawings define the proposed building and technical information. The BOQ records work items, quantities and prices.

Before signing, the parties should be able to match the project name, site, drawing revision, material descriptions, units, quantities and totals across the documents. Where a product is to be selected later, the contract record should identify the allowance or reference price, the approval process and the way any change will be documented. A sales rendering or an informal message is not a substitute for an agreed written scope.

Prospective clients can review Greenery’s house designs and completed-project portfolio when preparing questions for a scope and specification meeting.

Payment milestones should correspond to verifiable completed work

OCPB states that payment instalments should correspond to work that has actually been completed. The useful question is therefore not only how many payments appear in the schedule, but what evidence is required before each one becomes due.

Foundation work, structural work, roofing, building services and finishes can each require different inspection records. The contract should state the completion criterion and the person or role authorised to confirm it. Owners should keep the signed contract, quotation, BOQ, receipts, approved change orders, site photographs and milestone records together.

In separate consumer guidance dated 4 July 2025, OCPB advised consumers to examine the work scope and first-payment terms carefully. It also recommended checking the contractor’s history, previous work, reputation and registered capital. These checks provide information; they do not eliminate project risk.

Warranties and delay provisions need operational detail

OCPB’s 11 May 2026 explanation states that the contract must address warranty periods and summarises a minimum five-year period for the structure and at least one year for other attached components. A usable contract should also state when the period starts, what work it covers, how a defect is reported and how the contractor will inspect or respond.

OCPB also says that the contract should contain a daily delay-penalty provision. The percentages shown in the agency’s news item are examples, not a universal statutory rate for every agreement. The actual contract should define the rate, the start point, extensions of time and the notice process. Parties should obtain case-specific legal advice where the wording or applicable law is uncertain.

New construction and alteration work are not the same category

OCPB distinguishes the 2016 controlled-contract framework for constructing a new residential building from the 2023 rules concerning evidence of payment for residential alterations, repairs and improvements. A form designed for one type of work should not be assumed to cover the other without checking the actual scope.

For a Chiang Mai or Lamphun custom-home project, the documents should make clear which work is included in the main contract, which work will be delivered by separate specialists and who coordinates the drawings, approvals, programme and inspections.

Pre-signing checklist for a custom-home contract

1. Confirm the contracting entity and the authority of the signatory.
2. Attach the agreed drawing set, specifications and dated BOQ.
3. Record included work, excluded work and interfaces between contractors.
4. Link each payment to work that can be inspected and documented.
5. Use a written change-order process for price and time adjustments.
6. State the commencement basis, programme, extension events and delay notices.
7. Define warranties, reporting channels and response procedures.
8. Keep receipts, transfer records and meeting minutes in one project file.

Read more about Greenery Design & Construction, then prepare your project questions before you book an initial architect consultation. The initial consultation is free; it does not include free drawings or free house design.

Frequently asked questions

Can a BOQ replace construction drawings?

No. Drawings and specifications describe the proposed work, while the BOQ records quantities and prices. They should use consistent references and revisions.

How large should the first payment be?

The sources used here do not prescribe one percentage for every project. OCPB advises consumers to examine the first-payment terms carefully and to align payments with work actually completed.

Does a five-year structural warranty mean that no defect can occur?

No. A stated warranty period defines contractual responsibility; it does not guarantee that a defect will never occur. The scope, notice method and response procedure still need to be clear.

Is this an official English translation or legal advice?

No. This is an English-language summary of Thai public sources for general preparation. It is not an official translation and does not replace advice on a specific contract.

Sources

• Office of the Consumer Protection Board: warning before signing a home-construction agreement, 10 May 2026 (accessed 24 August 2026; Thai)
• Office of the Consumer Protection Board: explanation of controlled contracts for home construction, 11 May 2026 (accessed 24 August 2026; Thai)
• Office of the Consumer Protection Board: contract-law document index (accessed 24 August 2026; Thai)
• Office of the Consumer Protection Board: consumer guidance on hiring a contractor, 4 July 2025 (accessed 24 August 2026; Thai)

Note: This article provides general information only. It is not legal advice or an official English translation.