Thailand Personal Income Tax for Expats: PND.90 vs PND.91

If you have recently moved to Thailand or started earning income here, the Thai personal income tax system can feel unfamiliar and a little overwhelming. The forms have different numbers, the rules about who qualifies as a tax resident are not always obvious, and the consequences of getting it wrong are easy to underestimate. This guide is written for expats who are new to the process. It explains the two main personal income tax return forms in plain language, who needs to file each one, and what the basic rules look like in practice.

What Is Personal Income Tax in Thailand?

Thailand levies personal income tax on individuals through the Revenue Department. The tax is calculated on assessable income earned during a calendar year, running from 1 January to 31 December. If you are considered a tax resident of Thailand, meaning you have spent 180 days or more in the country during that tax year, you are generally required to report income that is sourced in Thailand, and under rules that came into effect from the 2024 tax year onward, certain foreign income brought into Thailand may also be assessable. The 180-day rule is cumulative across the year and does not require the days to be consecutive.

The Difference Between PND.90 and PND.91

These two forms are both personal income tax returns, but they are designed for different situations. PND.91 is the simpler of the two. It is intended for individuals whose only source of assessable income during the year was employment income under Section 40(1) of the Revenue Code, which is essentially salary paid by a single employer. If your tax situation is straightforward and your income comes from one job with one employer who has been withholding tax on your behalf throughout the year, PND.91 is likely the form you need.

PND.90 covers a much wider range of income types. If you have income from more than one employer, freelance or consulting fees, rental income, business income, capital gains, dividends, or other sources beyond a single salary, you must file PND.90. Most expats running their own businesses or working in Thailand in any capacity beyond a single salaried role will find that PND.90 applies to them.

Who Must File a Return?

Not every person in Thailand is required to file a personal income tax return, but the threshold is relatively low. As a general rule, if you are a single taxpayer and your total assessable income from employment sources exceeds 120,000 baht per year, you are required to file. If your income comes from other sources such as business or rental income, the threshold is 60,000 baht per year. For married couples, different combined thresholds apply. These figures are based on gross assessable income before deductions, not your taxable income after allowances have been applied, so it is worth checking even if you think your taxable amount might be close to zero after deductions.

It is also worth noting that being required to file is a separate question from whether you will owe tax. It is entirely possible to be required to file a return and still receive a refund, particularly if your employer has been over-withholding during the year. Filing is still mandatory regardless of the outcome.

What Income Is Actually Assessable?

Thailand uses eight categories of income under its Revenue Code, and the category your income falls into determines how deductions are calculated. Employment salary falls under Section 40(1). Director's fees and consulting income often fall under Section 40(2). Business income, rental income, and investment income each have their own sections with their own deduction rules.

For expats, the question of foreign income has become more important since the Revenue Department issued guidance in late 2023 clarifying that income earned overseas and remitted to Thailand in the same tax year it was earned would be considered assessable. This marked a change from the previous interpretation many people had relied on, which focused on the year of remittance rather than the year the income was earned. If you are bringing overseas income into Thailand, this is an area where taking professional advice is particularly worthwhile, as the rules continue to evolve and your personal situation will determine how they apply to you.

Key Deadlines to Know

Personal income tax returns for a given calendar year are typically due by the end of March of the following year when filing a paper return. For online filing through the Revenue Department's e-filing system, the deadline is usually extended by eight days, placing it in early April. For the 2024 tax year, returns would normally be due in March or April 2025 depending on how you file.

Missing the deadline can result in a surcharge of 1.5 percent per month on any outstanding tax, and there is an additional penalty of 100 to 200 baht for late filing even if no tax is owed. These amounts may seem modest, but late or missed filings can create complications with work permit renewals, visa applications, and company director obligations, so it is worth treating the deadline seriously.

How to Actually File

You can file your personal income tax return online through the Revenue Department's website at rd.go.th, or you can submit a paper return at your local Revenue Department office. Online filing requires a taxpayer identification number, which is a 13-digit number issued by the Revenue Department. If you do not already have one, your employer may have registered you, or you may need to apply in person at a Revenue Department office with your passport and proof of address.

The online system is available in Thai, which can make it difficult to navigate if you are not fluent in the language. Many expats choose to work with a local accountant or tax advisor to prepare their return, particularly if their income situation involves multiple sources, foreign remittances, or deductions that require documentation.

Common Deductions and Allowances Worth Knowing

Thailand's personal income tax system includes a range of deductions that can significantly reduce your taxable income. Employment income earners can deduct 50 percent of their income up to a maximum of 100,000 baht as an expense deduction. There are personal allowances for the taxpayer themselves, for a spouse, and for dependants such as children and parents. Contributions to a registered provident fund, life insurance premiums, and investments in certain government-approved savings schemes may also be deductible within prescribed limits. Keeping documentation for all of these is important, as the Revenue Department can request evidence to support the figures you report.

Understanding the basics of which form applies to you, whether you meet the filing threshold, and when the deadline falls is the essential starting point for getting your Thai tax obligations right. If your situation is anything other than a single salary from one employer, it is worth speaking with a qualified accountant before you file.