Why a Separate Thai Will
A home-country will (US, UK, EU, AU) is technically valid in Thailand under CCC §1655 if executed under the law of the testator's nationality — but recognition requires the will to be probated in the home country first, translated, MFA-legalized, and then re-probated in Thailand. That process takes 12-24 months and costs THB 200,000+ in translation and legal fees.
A parallel Thai will covering only Thai-situs assets bypasses that entirely: it goes straight to Phuket Provincial Court, is probated in 3-6 months, and lets your executor deal with the condo, bank account, and vehicle without waiting for home-country probate.
