You do need a personal bank account for the application (doesn't need to be on a Thai bank). Also, you're not allowed to run a company in Thailand on the DTV, either. (Ignore the last sentence if the company is not registered in Thailand, but elsewhere).
I don't have the screenshot here, but when I applied online it was written in big uppercase red letters that even if they SUSPECTED I had left Korea (where I applied), they would cancel my application. I'm sure it's still written somewhere on the Embassy website, will upload later if I find it.
that's not what the rules say. The rules are clear. Yet many have been able to do what you say without trouble, many others have been called for an interview even after they left the other country.
should include that on your original post, as some visas can't be obtained inside Thailand. Also, age and job (if any) would help, as there are age-tailored visas here, also.