You cant do any border crossings on a 60 day single entry tourist visa. That's because it is what it says - a *single entry. One in, none out until you leave.
If you leave before the 60 days, the visa immediately ceases. You can't just leave and come back a few days later because you've forfeited those other days.
I think you could be referring to what Thai immigration call 'out/in' - a 30 day visa exemption (you're US so eligible) which is extended for a further 30 days making 60.
Then you leave the country for a short while (some go for 5-7 days but some just leave in the morning of day 1 and return that afternoon) and go to Laos or Cambodia then get another 30 day exemption stamp when you return. If you are lucky, they will allow the second, but that's your lot for the year.
Better to get an METV (Multiple entry tourist visa) in your home country which will get you up to 9 months if you play it right.
os or Cambodia or Penang and apply for a second one at the Thai embassy/consulate there but there's a chance it'll be refused on the grounds you aren't a real tourist.
Long term, you'd be better trying for a 12 month ED visa and say you want to study muay Thai or Thai language and culture.