Do denials of entry (because of too many tourist visas or visa exempt entries) seem to happen more often at airports than at land borders?

I am wondering if it's better to fly to a nearby country like Malaysia and enter Thailand overland instead of flying directly into Thailand.

Even though I haven't been in Thailand for 1.5 years now, I have entered visa exempt quite a few times in the years before that and am worried about being forced to fly back home, since I read about so many people being denied entry recently (especially at airports?).

Is there a rule about a maximum of days per year one can spend in Thailand using visa exempt?