The Thailand tourist visa is usually valid for three months from date issued, for a stay up to 60 days.
Extension of Stay:
Those who wish to stay over 60 days or may wish to change their visa type while in Thailand must file an application for permission at the Office of Immigration Bureau located on Soi Suan Plu, off South Sathorn Road, Bangkok 10120, Tel (662) 287 3101 to 10 or at www.immigration.go.th.
The extension of stay as well as the change of certain type of visa is solely at the discretion of the Immigration Officer.
For double entry visa - available for tourist visitors only - consular fee is double (request for more than one entry should be made in writing with the application form).
Your application will be checked and hand carried to the Consular office, and is usually processed in 1-2 business days.