Thai accounting and audit requirements

The mandatory annual audit

Thailand has no small-company audit exemption for limited companies. Every Thai limited company must have its annual financial statements audited by a certified Thai auditor and filed, dormant companies included. The annual cycle is fixed by law: the financial statements must be approved by a shareholders' meeting within four months of the fiscal year end, and filed with the Department of Business Development within five months, with a separate corporate income tax return filed with the Revenue Department within 150 days of year end. A mid-year corporate tax prepayment filing is also required, based on a projection of the year's profit, and materially underestimating that projection attracts penalties. Late or missed filings bring fines for both the company and its directors, and a pattern of non-filing can lead to the company being struck off and to complications for the directors' immigration status, since work permit and visa renewals lean on the company's filed accounts.

TFRS in brief

Thai accounting standards come in two tiers. Publicly accountable entities, listed companies and the like, apply full Thai Financial Reporting Standards, which track IFRS closely. Everyone else, meaning the overwhelming majority of foreign-owned companies here, may apply TFRS for Non-Publicly Accountable Entities, a deliberately simpler framework: broadly historical-cost accounting with fewer disclosure demands and without the heavier IFRS machinery. For a foreign group consolidating a Thai subsidiary, the practical point is that local NPAE accounts may need adjustment to group IFRS or US GAAP policies at consolidation, which is routine but should be agreed with the accountant at engagement, not discovered at year end.

Bookkeeping standards and obligations

• Books must be kept in Thai, or in another language with a Thai translation available, and accounts are maintained in baht.
• A bookkeeper meeting statutory qualifications must be responsible for the accounts; in practice this is your accounting firm.
• Records must be retained for at least five years, and longer retention is prudent where tax positions remain open.
• Monthly compliance runs alongside the annual cycle: withholding tax filings, VAT returns for registered companies, and social security filings each month, so a Thai company has a filing obligation almost every month of its life.
• Supporting documents matter disproportionately; Thai tax practice is document-driven, and an expense without a proper tax invoice in the prescribed form is routinely disallowed.

The audit itself is usually a lighter-touch exercise than a UK or US audit for a small company, but it is not a rubber stamp, and auditor independence rules mean your bookkeeper and auditor must be genuinely separate. Budget for both: for a small, clean company, bookkeeping plus audit typically runs from several tens of thousands of baht a year upward, scaling with transaction volume and complexity.

Choosing an accountant

The accountant is the most important early hire a foreign-owned Thai company makes, because immigration renewals, banking and BOI compliance all draw on the accounts they produce. The selection criteria that matter: genuine experience with foreign-owned companies and the DBD's evidentiary expectations, including the bank-statement capital proof rules applying to Thai shareholders in foreign-participation companies from 2026; English reporting capability at the standard your group requires; a monthly closing discipline rather than a shoebox reconstruction each spring; clear separation from, but coordination with, the auditor; and the capacity to support a Revenue Department query, which is a matter of when rather than if for companies with foreign transactions. Fee differences between firms are small against the cost of a bad year-end or a failed work permit renewal; choose on competence and responsiveness.

Transfer pricing documentation obligations apply to related-party dealings above statutory revenue thresholds, and Thai subsidiaries billing or paying overseas affiliates should raise this with their accountant early rather than at audit time.

Setting the function up properly

The pattern that works: engage the accounting firm before incorporation so the chart of accounts, VAT registration decision and payroll setup are right from the first month, calendar the full filing year in advance, and have the accounts reviewed against immigration and BOI requirements, not just tax ones. Asia Global Partners maintains a short list of accounting and audit firms we trust with clients' companies, matched to the size and sector of the business, and we coordinate their work with the immigration and corporate lawyers so the company's paper position is coherent everywhere it is examined. Thailand's steady move to electronic filing, e-tax invoices and data-matched Revenue Department systems only raises the value of getting the bookkeeping architecture right at the start, because inconsistencies that once passed unnoticed are now surfaced by software.

This briefing is general information, not legal, tax or investment advice. Thai rules change frequently and individual cases differ. Verify current requirements with the relevant authorities, including the Immigration Bureau, the Board of Investment, the Land Department, the Department of Business Development and the Revenue Department, and take advice on your own facts before acting.