Okay,
@Ma**
, I think you're not understanding what a re-entry permit does. When you entered thailand on a single entry tourist visa you were stamped in for 60 days.
If you want to exit the country and return within those 60 days you could buy a re-entry permit. It WON'T give you more time on the 60 day stamp, but it will let you exit/re-entry the country and get stamped in with the original admitted until date you got when you first entered. A re-entry permit does NOT add any days to the time you're allowed to stay here.
You usually get a 30 day extension ONCE on a 60 day tourist visa at the immigration office for 1900baht