BOI vs Treaty of Amity vs Thai LLC: A 2026 Decision Tree for Foreign Founders

Honestly, this is the question we get on every first call: Thai limited, BOI promotion, or — if you're American — Treaty of Amity? On the pitch deck all three look the same. In practice they are not even close. The difference shows up in foreign-ownership ceiling, which sectors you can actually operate in, how much capital is locked up, how much tax you pay, and how long you wait to be operational.

The baseline rule under the Foreign Business Act B.E. 2542 (1999): any company with 50% or more non-Thai shareholding is "foreign," and foreign companies are restricted from most service, retail, and trading activities unless one of the carve-outs below applies. This guide walks the three live options in 2026 and ends with a decision tree you can actually use.

What Each Option Actually Means

Standard Thai Limited Company. Registered with the Department of Business Development (DBD) under the Civil and Commercial Code. Foreign ownership is capped at 49% in any activity that falls under FBA List 2 or List 3 (ASEAN Briefing on FBA restricted sectors). The remaining 51% must be held by Thai nationals — and since January 2026, those Thai shareholders must produce three months of bank statements proving real capital contribution under DBD anti-nominee rules (Lex Bangkok 2026 guide).

BOI-Promoted Company. A company granted an investment promotion certificate by the Thailand Board of Investment. BOI promotion unlocks 100% foreign ownership, land ownership rights, streamlined work permits, and — depending on category — corporate income tax holidays of 3 to 13 years. The minimum project capital is THB 1 million excluding land and working capital, and value-added must hit at least 20% of revenues for most sectors.

Treaty of Amity Company. Available only to US citizens and US-majority entities under the 1966 Treaty of Amity and Economic Relations. Allows up to 100% American ownership in most sectors, with the company registered as a standard Thai limited company first, then certified by the DBD after the US Embassy in Bangkok issues a citizenship letter (Acclime guide). Minimum capital is THB 2 million for non-restricted activities or THB 3 million per restricted activity (Siam Legal).

Cost & Timeline Comparison

Structure	Gov Fees	Typical Pro Fees	Timeline
Thai LLC (49% foreign)	~THB 6,500—7,500 for THB 1M capital	THB 30,000—80,000	5—15 working days via DBD Biz Regist
BOI-Promoted	DBD + BOI filing	THB 150,000—500,000+	60—90 days
Treaty of Amity	DBD + ~USD 365 US Embassy	THB 80,000—200,000	4—12 weeks total

Since 1 January 2026, all private limited company registrations must run through the digital DBD Biz Regist platform — paper filings are no longer accepted.

Which Sectors Allow Which Structure

The FBA splits restricted activities into three lists:

• List 1 — strictly prohibited to foreigners (newspaper, broadcasting, rice farming, land trading). No structure unlocks these.
• List 2 — affects national security, arts, natural resources. Requires Cabinet approval; BOI promotion can override.
• List 3 — sectors where Thai businesses are "not yet ready to compete": most professional services (legal, accounting, architecture, engineering), retail with capital under THB 100M, wholesale, advertising, hotels, and most B2B consulting. This is where the majority of foreign founders get stuck.

A Treaty of Amity company can operate in nearly all List 3 sectors as a US-owned entity, with several notable exclusions: communications, transport, fiduciary services, banking, land / natural resource exploitation, and domestic trade in agricultural products (H&P Law Firm). BOI promotion provides foreign ownership relief only for the promoted activity itself — not the whole company's revenue mix.

Tax Implications — Where BOI Wins

A standard Thai LLC and a Treaty of Amity company both pay the headline 20% corporate income tax with no holiday. BOI is the only route to a tax break.

BOI categories tier the exemptions:

• A1+ — up to 13 years Corporate Income Tax exemption, uncapped. Frontier tech, biotech, advanced materials, EV cell manufacturing, AI R&D centres.
• A1 — 8 years Corporate Income Tax exemption, uncapped. High-tech R&D, advanced electronics, key S-curve manufacturing.
• A2 — up to 8 years Corporate Income Tax exemption, capped at investment. Software development, digital platforms, data analytics (Category 8.1.1), cloud services, electronic design (AIM Bangkok on BOI digital incentives).
• A3 — 5 years Corporate Income Tax exemption. Lower-priority knowledge-based and advanced industries.
• A4 — 3 years Corporate Income Tax exemption.
• B1 / B2 — no Corporate Income Tax holiday, but foreign ownership and work permit privileges retained.

BOI-promoted companies are also exempt from the standard 4:1 Thai-to-foreign employee ratio and from import duties on machinery — material savings for any capex-heavy operation. PwC's Thailand tax summary confirms the framework.

The 2026 Decision Tree

Walk these in order:

1. Is your activity on FBA List 1? Stop — no structure works.
2. Are you US-passport-holding or US-majority-owned, and your business is professional services, consulting, software services, or B2B? Treaty of Amity wins. You get 100% ownership in ~6 weeks for under THB 250K all-in, with no Thai shareholder needed.
3. Are you in tech, digital platform, manufacturing, R&D, EV, biotech, or a recognised S-curve sector — and willing to commit ≥ THB 1M capex with a real Thailand operation? BOI. The 3—13 year tax holiday alone justifies the longer timeline, and you keep 100% ownership.
4. Are you small, bootstrapped, in a List 3 service business, and not American? A 49/51 Thai LLC with a vetted local partner remains the fastest legal path — but plan the shareholders' agreement and preferred-share structure carefully under the 2026 anti-nominee rules.
5. Manufacturing, but small scale? Run both BOI and Thai LLC scenarios. If you clear A2/A3/A4, BOI almost always wins on multi-year cash terms.

The wrong structure is expensive to unwind — share transfers trigger stamp duty, BOI revocation claws back tax holidays, and Amity certification doesn't transfer to non-US acquirers. Get this decision right at incorporation, not at Series A.