My advice is to go back and finish your ed visa. Then go to one of the near by countries, maybe Vietnam or Indonesia, and apply for your dtv there.

That way you can max out your time in Thailand, your ed visa is finished and you won’t have any overlapping visa issues. You don’t have to cancel any flights and you have more time to prepare your documents for the application.

You need to physically go down to cancel your ed visa anyway so that requires you to go back.