@Brandon ***********
The DTV was not created by law. Under the existing law the Ministry of Foreign affairs has the right to create and categorise and withdraw visas. There was no "law" to create the DTV or any specific visa. It is not required as the ministry already holds the power. Instead it was created by a ministerial regulation. The DTV is basically a policy under the existing law it is not enshrined in or mentioned in any law. It is not considered a long term immigration type visa but a temporary visitor visa even though longer term and for that reason treated "like a tourist visa". In the ministerial regulation that creates the DTV Order No.
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I have not been able to find the word "tourist" using several possible Thai variations although there are quite a few words in the documents I can not translate and do not have a searchable version. It does seem however the classification as a tourist visa has more to do with the nature of the visa and is an interpretation rather than any specific wording in the ministerial regulation.