Will I face issues re-entering Thailand on a visa-exempt status after leaving on a Non-B visa?

If leaving by air, would he be stopped from leaving??? Would he just have trouble getting another extension if he didn't cancel this one?

you've not been on ANY visa 🙁 you've been on yearly extensions of stays (look at your stamp)

You need to cancel that extension at the immigration office that issued it, then you can exit the country.

You might be questioned on why you're comin' back in free stamp (60 day visa exempt) after comin' off 3 years of non-B extensions but you should get in okay.

Worst case they'll ask you to prove you're leaving thailand within the 60 days you'll be stamped in for. So having proof of onward travel will help IF you're questioned when you stamp in.

I would wager you'll get in just fine.. Best of luck with it