500 baht fine, no problem now unless they stop you somewhere other then imigration and if they do 5 year ban from Thailand, reports say they are randomly stopping peoble in parking lot and inside airport to check you before you get to Imigration
Besides that overstay are in the computer so no one knows if it will get you in problems in the future
i know what your saying, i am just pointing out that the fact your saying it/ that they did not ask last time by no means mean that they will not ask today/ tomorrows and on
So no matter what to be more safe allways bring 20.000 baht in cash