What happens if I report my visa overstay to Thai immigration and can't pay the fine?

Okay let's sort out exactly how it works when you "turn yourself in" on overstay <- as in you don't have the funds to pay the fine you ran up by overstaying.

You will get arrested, transferred to IDC <- immigration detention center. They will hold you there until you see a judge, the judge will waive the overstay fine and charge you between 3 and 5 K baht <- there is no way out of that at all. You'll get banned for 5 years <- there is no way out of that either.

They will then take you back to IDC where you will be held until your flight out, they will take you in a van to the airport <- that used to cost 800 more baht <-there is no way out of that either

You also have to fly back on an approved carrier <- one that takes deportees back to your country, <meaning you can't just pick a flight you want with an airline you want.

That's it, you stay out of the country for the 5 years until the ban/blacklisting runs out and you can come back no problem.