That wasn’t my experience. I had been doing border runs for 20 months went back to America for a few months before applying and got approved. I guess one could argue that those 2-3 months outside of Thailand could make a difference.
I booked an appointment with Bangkok hospital and then emailed them asking for an official letter of appointment for the Thai consulate as they requested it for a visa. They produced a generic letter stating my appointment details and it worked.
another benefit of DTV is you can leave and come back easily rather than education visa they don’t want you to leave the country and will most likely question upon reentry and possibly deny you. At least from what I’ve read on these forums.