@Tod ********
it was in the details of the DTV published in the Royal Gazette - Section 5 Aliens and their dependents who have been granted a special tourist visa (Destination Thailand Visa: DTV) and later wish to change the visa type or apply for a visa to temporarily stay in the Kingdom for other purposes may do so and the original special tourist visa (Destination Thailand Visa: DTV) shall be invalid. However, consideration of permission to change the visa type and to temporarily stay in the Kingdom for other purposes shall be in accordance with the criteria, methods and conditions set by the Immigration Bureau.