Can I get a 180-day stamp after my DTV course expired without renewing?

The DTV multiple visa is valid for five years. There are no restrictions on entering or leaving Thailand. Each stamp in your passport allows you to stay for up to 180 days. If you stay in Thailand for exactly 90 days, you must notify immigration about your stay.

You do not have to worry about using Digital Nomads, Soft Power, or Spouse. The immigration checkpoint will not require anything. They can see in their system that you have a valid DTV visa.

No need to reapply. Muay Thai course wasn't gonna last 5 years anyway. Just maintain THB 500k all the time and say you're remote worker, but better have stuff to back that up if they insist on checking.

Unless it says Muay Thai in the remarks then it's no different. Just say you're a remote worker IF you get questioned.

No need unless buying an in country extension. That said, you should prepare yourself for possible questions upon re-entry, do not say your course is finished, state you are a remote worker and possibly prepare some portfolio of work contract proof etc. You have the visa and it's good for 5 years.

That is a FAQ, so scroll or search the group, as you should always do before asking a question.