@Seth ***********
, face it your parents aren't the first foreigners to overstay their visas. They probably got an "admitted until" stamp of the 4th of March, is that right? If so they'll be on 8 days overstay when they go to the immigration office and owe 4000baht in overstay fines.
They can apply for the 30 day extension right after they pay the fines for 1900baht BUT that extension will start from the expiration date of their original stamp.
The immigration office doesn't care if they act contrite or say they didn't know or even if they know how to do the action known as the "wai". Like I said your parents ain't the first foreigners to overstay here. They just want tme to pay their fines, get their extensions and be on their way.