Leaving from our lovely new airport on Sunday I saw a sign at immigration which basically said that overstay fines now start at Baht 1,000 and are Baht 500 for every day thereafter (up to the maximum, which I think is Baht 20k).
I had not realised till then that the minimum overstay fine was Baht 1,000 (thought it was Baht 500).
As it happens, overstay has never been an issue with me, but might be worth thinking about if this is something that is likely to affect you.