Last year, the Thai Revenue Department issued updates concerning how both local and foreign income is taxed in Thailand. Therefore, in 2025, understanding your Thailand tax obligations as a foreigner and how to fulfill them has become more important than ever to avoid overpaying or accidentally incurring civil or even perhaps criminal penalties in Thailand.
In this article, we will cover the key deadlines revolving around personal income tax in Thailand, the tax requirements, and how you can successfully file your tax return in Thailand.
When Is Thai Tax Season?
The Thai tax season comes directly after a Thai tax year ends. A “tax year” is the same as a calendar year, and encompasses all the taxable income earned from January 1 to December 31. Once the Thai tax year ends, individuals who are liable to file a personal income tax return will need to do so in a set timeframe, also known as a Thai tax season. The deadlines will vary based on the method of filing, as shown below:
- Hard copy: Submit the paper tax returns to the Revenue Department area office by March 31st.
- E-filing: Submit tax returns electronically through the Revenue Department’s official website by April 9th.
If you fail to file your return by the Thai tax deadline, you may incur fees or even face prosecution if the Thai Revenue Department suspects tax fraud.
Do I Have to File a Thailand Tax Return as a Foreigner?
Your obligation to file a tax return in Thailand is determined by factors such as your residency status, sources of income, and the newly updated foreign income rule.
Tax Resident Rule
A foreigner is considered a tax resident in Thailand if they have spent 180 days or more in the country during a calendar year. Tax residents must file a tax return for both income earned in Thailand and income brought into Thailand from overseas within the same tax year.
The New Foreign Income Rule
Under the recent regulation update, all foreign income earned after 2023 that is brought into Thailand is now taxable. This means that if a foreigner earned income overseas in 2024, but brought it into Thailand in 2025, that income will still be subjected to Thai income tax.
Before, foreigners could earn foreign income in a tax year and simply wait until the next tax year to bring it in and avoid income tax, but this loophole has now been closed. As long as the income was earned in 2024 or later, it is taxable as soon as it is brought into Thailand, regardless of when that will be.
Important Tax Rules Foreigners in Thailand Should Know
When preparing to file your tax return in Thailand, it is important to keep the following rules in mind, as they will help you avoid unnecessary financial penalties later on:
- Progressive Tax Rates: Thailand’s income tax rates range from 5% to 35%, with your tax bracket depending on the amount of income you earn from January 1st to December 31st.
- Taxable Income: “Taxable income” includes salaries, business income, rental income, pensions, and now foreign income brought into Thailand.
- Allowances and Deductions: You may be eligible for certain deductions based on income and expenses as outlined by Thai tax laws. To learn more about this, consult with a tax professional in Thailand for specific details.
- Double Tax Agreements: Thailand has Double Tax Agreements with several countries to prevent double taxation. These agreements may allow you to avoid being taxed twice on the same income, depending on the terms outlined in the specific treaty between Thailand and your home country.
- Penalties for Non-Compliance: Failure to file a tax return or filing an inaccurate one by mistake will incur financial penalties and fees. Filing a false tax return or otherwise deliberately trying to evade taxation may lead to civil and perhaps criminal penalties in Thailand.
How to File a Tax Return in Thailand as a Foreigner
Filing a tax return in Thailand can be done online or in person, with each method offering its own advantages and challenges. But before you file your tax return for the first time, ensure you have a Thai Tax Identification Number (TIN) so that you are registered in the Revenue Department system. Without one, you cannot file, and may still incur penalties for late filing.
In-Person Tax Filing
Foreign taxpayers can file their returns in person at the Thai Revenue Department office that has jurisdiction over their region of residence. However, English-language services are not guaranteed, and officials generally do not assist with calculating deductions, credits, or taxes owed. Because of this, it is important to make sure that all the necessary calculations are done before visiting the office. You should also bring a trusted interpreter if you cannot speak fluent Thai.
Online Tax Filing
The simplest way for a foreign taxpayer to file a tax return is through the Thai Revenue Department’s web portal. This platform provides services in English, making it accessible to non-Thai speakers. However, the translations aren’t ideal, and the system can be confusing for those with complex tax situations such as multiple income streams.
On the platform, users are required to manually separate their income sources and accurately input totals into the appropriate categories, as well as identify and apply for credits and deductions they believe they are owed.
Professional Income Tax Filing Services for Foreigners in Thailand
If you’re a tax resident in Thailand and are unsure about your tax responsibilities, get in touch with Siam Legal International. We are a full-service law firm and visa consultancy with over 20 years of experience in helping both local and foreign clients with their legal needs, including tax issues.
Our team of experienced local and international tax advisors will assist you in identifying which Double Tax Agreements, deductions, and tax credits apply to your situation, minimizing your tax liability through all legal avenues.
By partnering with Siam Legal, you can avoid potential legal issues during the tax filing season and eliminate the risk of accidentally committing tax fraud, all the while keeping more of your hard-earned money secure.
To begin the process of filing your tax return, determining your liabilities and credits, or registering for a TIN, do not hesitate to contact Siam Legal to book a consultation now!
