Do I need a Thai will if I have a will in my home country?

Strongly recommended yes — even if your home-country will is technically capable of disposing of Thai assets. The reason is procedural, not substantive: probating a foreign will in Thailand is slow, expensive, and uncertain, while probating a properly executed Thai will is routine.

Under Section 1620–1755 of the Civil and Commercial Code, succession to property situated in Thailand is governed by Thai law for real property and by the law of the deceased’s nationality for movable property. In practice, the Thai Probate Court (ศาลคดีมรดก) will require:

• The original foreign will, plus a certified copy.
• A certified Thai translation.
• An apostille or legalisation from the issuing country’s foreign ministry.
• A grant of probate or letters of administration from the home jurisdiction.
• An affidavit from a lawyer in the home country explaining the relevant succession law.

Expect this to take 9–18 months and cost THB 80,000–250,000 in legal fees and translation, before any disputed claims. During that period, Thai bank accounts are frozen, condos cannot be sold, and your family will struggle to access funds.

A Thai will, by contrast, is admitted under Section 1656 of the CCC and probated in 4–8 months at fees of THB 30,000–80,000. The five permitted formats (Sections 1656–1672) include a simple holograph (written entirely by hand), an “ordinary” will signed before two witnesses, and a public document executed at the Amphur. Most foreigners use the ordinary written form drafted bilingually.

Keep the two wills geographically separate: the Thai will should cover only Thai-situated assets and explicitly state it does not revoke the foreign will. The foreign will should mirror this. A well-drafted pair avoids the most common pitfall — accidental revocation.