If you have a valid tourist visa they will reject your DTV. Just cost me thousands of dollars for flights.
EDIT: I used the full 60 days on my multi-entry visa already hence assuming it wouldn’t be valid. Also assumed my flights would be useless if I have to return to the USA to apply.
EDIT 2: thanks for the suggestions about applying in Vietnam. Seems a bit dubious for that to be considered a “residence” though. I guess if it works it works though.