A business outside Thailand can register a .co.th with a trademark or company name and a representative in Thailand. This guide, checked against the T.H.NIC registration guideline of March 2026, explains the three routes, the documents, what changed in 2026, the naming rules, .co.th vs .in.th vs second-level .th (round 3 of 2026 open until 30 November), the expiry timeline and why there is no UDRP for .th.