So just to be very clear...If I have the DTV visa but I do not wish to activate it upon my entry to Thailnd because I'm planning a short stay, do I get to choose whether to use it and when or does it get activated by default once it's in the immigration computer data base?
TLDR : Answer Summary
Once you possess a DTV visa, it is automatically activated upon issuance by the embassy, not when you enter Thailand. Therefore, you do not have a choice to delay activation during your entry. Upon entering Thailand, using your visa will grant you a 180-day stay, regardless of whether your visit is intended to be short.
DTV VISA RESOURCES / SERVICES