Can I apply for a job in another country after receiving a DTV visa in Thailand?

You're from Myanmar, so I understand why you want to get out. You will be able to apply for jobs in other countries from Thailand, but remember, under the terms of your DTV you are meant to be working remotely, getting medical treatment, learning how to boil an egg. The potential problem you might face is obtaining a work visa. Depending on the country, that might be something you have to initiate from inside Myanmar. It might be complicated. The easiest country if you are a professional might be Singapore. You can get offered a job there, then have 6 months, in country, to get the work permit.

The DTV visa allows you to live inside Thailand but work outside of Thailand.

Yes, you can do as you please outside Thailand