@Chris ******
Money can be at any bank in the world, as long as it is the equivalent of 500K.
You have to prove you are legally in the country you apply from, that does not need to be your home country, but it cannot be Thailand of course.
For somebody now on a non-o visa it indeed might be difficult to comply with other DTV requirements, because the visa is not meant for those groups.
DTV gives you a tourist status in Thailand, which might mean rights you have with non-o might disappear.