Thailand Income Tax

Thailand income tax system combines a progressive personal income tax (PIT), a headline corporate rate (with special SME bands and incentive regimes), an extensive withholding regime, and newer rules that affect cross-border income (notably rules on foreign-sourced income remitted to Thailand and the OECD global minimum “top-up” tax). This guide explains who is taxable, how residency and source rules work, the current PIT/CIT picture, withholding and filing obligations, recent policy changes you must watch, enforcement priorities, and practical traps for individuals and companies operating in Thailand.

1. Who pays tax — residency and tax base

An individual is treated as a Thai tax resident if they reside in Thailand for 180 days or more in a calendar year. Residents are taxed on Thai-source income and, in certain circumstances, on foreign-sourced income when it is brought into Thailand. Non-residents are taxed only on Thai-sourced income. For companies, Thailand taxes Thai-sourced profits of resident juristic persons and certain Thailand-source income of non-residents.

2. Personal Income Tax (PIT) — rates, allowances and taxable income

Thailand uses a progressive PIT scale. The bands currently run from 0% up to 35%, with the basic structure as follows (net taxable income, THB): 0–150,000 exempt; 150,001–300,000 at 5%; 300,001–500,000 at 10%; 500,001–750,000 at 15%; 750,001–1,000,000 at 20%; 1,000,001–2,000,000 at 25%; 2,000,001–5,000,000 at 30%; over 5,000,000 at 35%. Standard allowances (personal, spouse, child, pension/insurance caps) and employment expense deductions reduce taxable income.

Taxable categories include employment income, business/professional income, rental income, dividends (subject to credit rules), interest, royalties and capital gains (with special rules). Many routine items are subject to withholding at source (see below), which operates as an instalment of final tax or as a prepayment.

3. Corporate Income Tax (CIT) and incentives

Thailand’s headline CIT is 20% for many companies, with preferential bands for small/special-purpose entities and generous incentives under the Board of Investment (BOI) for promoted activities (tax holidays, import-duty relief, etc.). The BOI remains an important route to reduce effective tax for qualifying projects. At the same time Thailand has adopted the OECD’s global minimum tax rules: a 15% top-up tax applies to large multinationals (thresholds aligned with the OECD) effective under Thailand’s implementation timetable. This means globally large groups may face a domestic top-up to ensure a 15% minimum effective tax.

Practical consequence: for normal resident companies the 20% headline remains the day-to-day rate, but multinationals and incentivized firms must model interactions between BOI exemptions and the top-up regime.

4. Withholding taxes (WHT) — common rates and temporary reliefs

Thailand operates an expansive withholding regime on employment, services, royalties, interest and dividends. Typical statutory WHT rates are in the order of 10–15% for many payments to non-residents (e.g., interest and royalties commonly 10–15%; dividends 10%), while resident service fees often have lower statutory WHT (and employers withhold payroll tax on wages). Importantly, the government introduced temporary reductions to certain WHT rates for payments remitted via the e-withholding system through 31 December 2025, which taxpayers and payroll teams should monitor for specific-rate changes and eligibility. Treaties can reduce final WHT via relief at source or refund procedures.

5. Foreign-sourced income and remittance rules — recent and important change

A critical development for expatriates and cross-border earners is the Revenue Department’s evolving guidance on foreign-sourced income remitted into Thailand. Draft rules and public guidance in 2024–2025 introduced a practical window under which foreign income brought into Thailand within the same or the immediately following year may be treated differently from older remittances — i.e., remitted income that arrives late may become taxable on remittance. The measures are in flux and proposals have been published giving grace-period style reliefs, but the final administrative rules and implementation details are subject to Revenue Department regulations. In short: do not assume offshore income is always tax-free when brought into Thailand — plan remittances with tax advisers and track the year of earning vs year of remittance.

6. Filing, payment and key deadlines

Individuals file annual PIT returns (forms PND90/91 or e-filing) for the calendar year; filing windows vary slightly by year but the Revenue Department has used late March/early April deadlines for paper vs e-filing in recent seasons — check the current year calendar. Companies file CIT returns with instalment payments (monthly/quarterly withholding and corporate instalments) and an annual final return. Late filing or payment attracts interest and penalties. For 2025 the Revenue Department and practitioner sites listed March/April filing deadlines for individual returns — verify dates each year.

7. Enforcement, audits and transfer pricing

Thai tax authorities have intensified audits on: (a) remitted foreign income, (b) proper withholding and e-withholding reporting, and (c) transfer pricing for related-party transactions. Large cross-border groups must maintain contemporaneous transfer-pricing documentation and be ready for audits that can reassess taxable income, apply penalties and trigger criminal investigations in egregious cases. Use robust documentation (contracts, bank trails for remittances, e-withholding receipts) and keep tax and accounting records to support positions.

8. Practical planning points and traps

Residency timing matters — 180 days is a hard planning threshold. Track days precisely.
Remit with care — if you expect to bring foreign income into Thailand, plan timing and documentation now given recent Revenue Department proposals.
Use treaties — Thailand’s DTA network covers many key jurisdictions; treaty relief can reduce WHT and double taxation.
Model BOI incentives vs top-up tax — companies using BOI holidays should test effective tax with the 15% minimum in mind.
Keep e-withholding discipline — the temporary WHT reductions require e-withholding reporting; payroll and AP processes must support the system.

Conclusion

Thailand’s income-tax system remains straightforward in headline terms — progressive PIT, a 20% headline CIT, and robust withholding and compliance rules — but recent policy moves make cross-border tax planning essential. The two items to watch closely are: (1) final Revenue Department rules on foreign-sourced income remitted into Thailand, and (2) the global minimum tax/top-up for large multinationals from 2025. For material personal or corporate cases engage a Thai tax adviser early: these rules interact with residency, treaty relief, BOI incentives and transfer pricing in ways that materially affect after-tax outcomes.