Filing a Thai tax return is not as complicated as it might seem from the outside. Most expats with straightforward income situations can file themselves online. This guide covers everything you need: the right form, the deadlines, and how to use the system.
Do You Need to File a Thai Tax Return?
You are required to file a Thai PIT return if you are a Thai tax resident (180+ days in Thailand in the relevant year) and you have assessable income exceeding the personal allowance threshold roughly 60,000 THB per year after deductions. In practice, most expats with any meaningful income should file.
Employees whose only income is from a Thai employer that has correctly applied payroll withholding may not need to file separately. However, if you have income from multiple sources, foreign income, or rental income, you should file regardless.
The Two Main Forms: PND 90 vs PND 91
| Form | Who uses it |
|---|---|
| PND 91 | Taxpayers with income only from employment (Section 40(1) income). The simpler form if you only have a salary from a Thai employer, this is your form. |
| PND 90 | Taxpayers with income from any other source, or from multiple sources. Most expats with foreign income, rental income, investment income, or self-employment income use PND 90. |
| PND 94 | Mid-year return due in September, required for certain income types (rental income, professional fees under Section 40(5) and (6)). Only required if you have these income types. |
Key Deadlines 2026 Confirmed Dates
| Return | Paper deadline | Online deadline (extended) |
|---|---|---|
| Annual PND 90 / 91 (for the 2025 tax year) | 31 March 2026 | 8 April 2026 (Wednesday standard extension confirmed) |
| Mid-year PND 94 (if required) | 30 September 2026 | 8 October 2026 |
The 8 April 2026 e-filing deadline falls on a Wednesday, so the standard 8-day extension applies with no weekend complications. File online to take advantage of the additional time.
Filing Online via the Revenue Department e-Filing System
- Go to rd.go.th the official Revenue Department website. Navigate to the e-Filing section. Use Chrome or Edge with auto-translate enabled for the best experience.
- Register or log in. First-time users create an account using their Thai TIN and passport details. You will receive an OTP to your registered mobile number.
- Select the correct form PND 90 or PND 91 depending on your income type (see table above).
- Enter your income details. Input income by category Section 40(1) for employment, 40(4) for investment income, and so on. Enter gross amounts before any withholding.
- Enter deductions and allowances. The system guides you through personal allowances, the employment deduction (50%, capped at 100,000 THB for Section 40(1) income), and other claimable items.
- Review the calculated tax. The system calculates your liability automatically. Enter any withholding tax certificates (Bor Orr Jor 50) to offset against the total.
- Pay any balance due. Payment can be made online via credit card or bank transfer. Overpayments are refunded to your Thai bank account.
- Download your submission confirmation. Save the PDF this is your evidence of filing.
Filing a Paper Return Where to Go
If you prefer or need to file on paper, PND 90 and PND 91 forms are available at any Revenue Department district office. Complete the form, attach supporting documentation (income evidence, deduction receipts), and submit in person by 31 March. Paper returns cannot be submitted at any Revenue Department office they must go to the office covering your district.
How to Pay Your Tax Bill
Online payment through rd.go.th accepts major credit cards and bank transfers via PromptPay. In-person payment is accepted at Revenue Department offices (cash or cheque) and at Krung Thai Bank branches nationwide (which act as payment agents for the Revenue Department). Payment must be made by the deadline to avoid interest and surcharges.
What Happens If You File Late or Don't File
Late filing incurs a surcharge of 100–200 THB plus 1.5% per month interest on any unpaid tax. Non-filing is a criminal offence under the Revenue Code, though prosecution of individual expats is rare. A more common consequence is difficulty evidencing tax compliance for visa purposes or when dealing with Thai banks. Filing a nil return (where you owe nothing) still provides the compliance record and avoids any technical non-compliance.
US Citizens Additional Obligations to the IRS
American expats must file a US federal tax return regardless of where they live. The deadline for overseas filers is automatically extended to 15 June (with a further extension available to 15 October by filing Form 4868). FBAR (FinCEN 114) must be filed electronically by 15 April (automatic extension to 15 October) if your foreign financial accounts exceeded $10,000 at any point in the year. These are separate from your Thai filing obligations.
Should You Use a Tax Consultant?
File yourself if: your income is employment-only from a Thai employer; you have simple foreign income with clear treaty protection; and you are comfortable navigating a partially-Thai-language government portal.
Use a consultant if: you have US dual-filing obligations; you have complex foreign income from multiple sources; you hold an LTR visa and need to correctly document your Royal Decree 743 exemption; or you have crypto gains, property sales, or other non-standard income. A good Thai tax consultant for expats typically charges 5,000–20,000 THB for a standard return, depending on complexity.