Thai people will scam you at any opportunity, it's just their nature and they can't help themselves...they they'll prey to Buddha and their karma will be clean again))
it depends on when your school will cancel your WP... Some are assholes and won't give you time until your flight. Why do you think that extension exists...?
If you gave one month notice does it mean you quit in the end of july? If yes, then your work will have to cancel your WP in the end of july as well, very simple. You can't cancel it yourself, they have to prepare all the papers and send someone from the office together with you. You could do it like a week before you fly out, then go to the immigration and apply for one week extension.
yes, they've mastered the art of sleeping, saw a dude sleeping ON his bike which was park directly in the sun, plus he was wearing leather jacket, literary, and it was in the middle of the day...they are not human beings, human sweat, thai people don't...