I think that only at Suvarnabhumi Airport one day of overstay is admitted and they don't charge 500 baht of penalty, but I also think that they mention the overstay day on the stamp
JD, you can confirm that multi entry non B visa is no more available for Non Shareholders to all Consulates of South East Asia or only in Malaysian Consulates?
Because after the initial Single Entry (90 days) Visa (B or O), it is possible to:
1) apply a multi entry visa (a sticker on your passport) valid 1 year that must be re-activate every 90 days leaving the Country (border run);
2) apply an Extension of Stay valid 1 year (a stamp on your passport) that allows you not to leave the Country but you need to report yourself every 90 days at Immigration office inside the Country