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All foreigners who apply for Tourist Visa at the Royal Thai Embassies and the Royal Thai Consulates-General worldwide, including eligible foreigners who apply for Visa on Arrival at designated checkpoints, will be exempted from Tourist Visa fee from  11  May B.E. 2553 (2010) to 31 March B.E. 2554 (2011).  Such arrangement is for Tourist Visa only.

Thailand passport and visa requirements – All tourists must possess a passport valid for at least 6 months beyond their intended length of stay (Retirement visa requires at least 18 months validity).

Foreign nationals visiting Thailand must possess valid passports or accepted travel documents and appropriate visas before entering the country. Visitors from several countries are permitted to stay up to 30 days without visas, while visitors from some other countries are entitled to apply for visas on arrival with stay of up to 15 days, provided they possess tickets confirming departure within 15 days at all ports of entry. Transit visas permit stay for up to 30 days and tourist visas for up to 60 days. Non-immigrant, diplomatic and official visas permit stay for up to 90 days. More info http://www.mfa.go.th/web/2637.php 30 and 90 Day Visa Exemption

Passport holders from most western countries do not require a visa when entering Thailand for tourist purposes if their stay does not exceed 30 days or 90 days . You must show proof of a confirmed return ticket and sufficient funds during your stay, which according to the Thailand Ministry of Foreign Affairs is a minimum of 20,000 baht per individual or 40,000 baht for a family (or equivalent in foreign currency). You may or may not be asked to show these depending on the discretion of the immigration officer.