In case anyone's still worried or hesitant about border-bouncing at Mae Sai, I just did one today with no problems at all, was exactly like pre-Covid.
I offered to show them my evidence of Covid vaccination, and they waved it away.
Seems like the latter might not be needed anymore - though I'd recommend bringing it if you have it.
Anyways, my photo evidence:
TLDR : Answer Summary
A user shares their recent experience of border bouncing at Mae Sai post-Covid, highlighting that the process felt similar to before the pandemic, with no issues encountered. They suggested carrying proof of Covid vaccination, although it was not requested by officials during their crossing.