If it was granted (which would be an illegal application anyway,) when you leave they will see you weren't stamped in on it. Be daft to be banned from the country for trying to cheat the system.
It's their country. Break the rules and suffer the consequences. Don't listen to other 'advice' on fb. If you are arrested and held in immigration prior to being deported and banned, the wi fi in the Bangkok Hilton is probably not too good if you want further advice then.
PC should be fine. I did mine last week, approved in 5 days, but I got a message at the end suggesting payment had not gone through. I left it, but all was OK.