Am I within my visa requirements if I leave Thailand on the last day of my visa extension?

Yes happen to me stamped overstay 1 day no fine

You should be passing customs before midnight for that flight so no problem, go through by 11pm chill with a coffee or beer before you board. Safe journey home

i did exactly the same: it was no problem. as stated above, you just need to go through the border control before midnight.

The way that works is you have until 11:59PM the day your stamp expires to stamp out of thailand, doesn't make a difference at all when you check in with the airlines it matters when you stamp OUT of thailand 🙂 that's when you're officially 'not in country'.

So if you don't stamp out by that time you'll 'technically' be on overstay, BUT that's fine because when you go to fly out by air overstays of under 24 hours don't pay the 500baht fine and you only get a small thai language only stamp in your passport near your exit stamp saying "overstay under 24 hours fine waived"

so either way you're fine.