What Are the Complications of Overstaying a 30-Day Tourist Visa in Thailand by a Few Hours?

Don't make a big deal out of it. You're not the first and for sure not the last tourist with a few hours overstay. Yes, overstay is something which need to be avoided, but let's keep our feet on the ground and use some common sense. If and that is a BIG IF there is a police checkpoint just before the airport, they will not arrest you when you show the ticket outbound and departure time a few hours later.

Good Luck

Just clear immigration before midnight

For future visits at the moment it only effect application of the Elite Visa and any visa application at the Thai Consulate in Penang.

if you leave by a land border you get a overstay stamp in the passport and the 500 Thb fine. If you leave by flight from international airport, normally the overstay stamp but no fine within 24 hours.

Well NOT

You could evoid it ...just beeing through the airport IMI before ...

No , no problem ..