Not the best advice, but personally if I got to 81 at the end of a 20 year Thai Elite, I'd consider just throwing my passport in the river and staying put.
I'll add that even as a frequent flyer with Oman Air, even when I have a valid visa they always check I have a return flight. Obviously all carriers are different, just my experience them them in particular.
, take no notice of the sad twats on here. Get to the airport, make sure you have 20k cash, be prepared to sign some paper, lose your 20k, and be banned for 1 year.
Don't get caught beforehand, it will land you with a 5 year ban.