@Conrad *******
, IF you are on an extension of stay based on employment that you got from the immigration office then BEFORE you try to stamp out of the country by land you need to go cancel it at the immigration office.
THEN you can go to a thai consulate in another country and BUY a single entry tourist visa <- that's what gets you stamped in for 60 days.
you cannot get a 60 day tourist visa at a land border, you need to GO to a thai consulate and get one.