unfortunately there has been a lot of abuse on the Visa exempt entries with lots of people trying to work on them. Therefore a few genuine tourists, as you may be, end up paying for them. Thailand is focused on short-term mass tourism, 10 to two weeks, a quick cash grab. Your thinking is correct and will give you peace of mind.
I agree it is random and that is difficult to deal with. In my opinion, granting another Visa exempt should also depend on the bank statements one can produce. If one can clearly finance a stay as a tourist, I see no issue