Is it acceptable to leave the country while applying for the DTV visa in Vietnam or Laos and then re-enter on a different visa?

The consensus among commenters is that if you apply for a DTV Visa in Vietnam or Laos, you are expected to remain in that country until your visa is either issued or rejected. Leaving the country could invalidate your application, as you won't be able to provide proof of your stay when required. If you return to Thailand on a different visa stamp after exiting the country where you applied, this may not be recognized by Thai immigration and could complicate your situation.