Straight to the airport. Don't get into trouble /arrested beforehand. Make sure you have the cash ready when you arrive at the airport immigration. Cash, apologetic behaviour and you should be fine.
Charge inventing is inevitable :) I know what you mean though. 1000 baht will feed a Thai family for a few days or so. Just chalk it up to experience. Always be on good terms with your employer here when you leave, visa transfer, work permits and an employer reference will still need to be done.
Not really, the clue is in the name, you are exempt from needing/using a visa, so they put a stamp in your passport, a no-need for a visa, visa exempt stamp.