Can I enter Thailand again on a visa exemption after leaving for Vietnam?

If you come by airplane it shouldn't be a problem, but as mentioned before, it all depends on the mood of the Immigration officer. If you want to make it sure try to get a Tourist visa there.

It's a 50 / 50 chance of being quizzed about your entries some IO on the day can be a little anal about things but they have to be seen doing their job even with a visa there is never a guarantee entry it's thailand we are talking about this year I have spent 24 weeks in total in thailand last entry was in July and was questioned about it why you here many time why you not get proper visa next time you have proper visa first time in 25 year ever been asked to see my ticket out showed him and he settled down Chokh di

I did 45+30 twice this year then I went to the states and got back 40 days later. The officer questioned me about my staying and he didn't look happy. Didn't get warned as I prove I was staying there just for a few days to pick my stuff and move to taiwan. He wanted to check my ticket and typed the data on his computer

Best chance would be to fly to Chiang Mai

Technically yes, however you may well be quizzed by Immigration so be prepared with the 3 proofs, ie 20k Baht in cash or a currency equivalent, accommodation, and onward travel within 30 days

No problem. Immigration may or may not ask some questions. Just doing their jobs. Who cares either way? Enjoy

I was qestioned back in August on my arrival because i had done the same think from January on this year

If you fly in you will have a chance but not guaranteed. Immigration is more tough in thailand after COVID

if you re not broke by now, you are not doing it right

As Jess said, Immigration may stop and question you if they think your trying to live here on extensions and exempt entries .

They may also take no notice, the risk is yours but a visa is a better option

Apply for a tourist visa in Vietnam if you want to be sure. It all depends on the immigration officer here with another exempt…