It's a SINGLE entry visa for a maximum stay of 60 days and even if you leave after just one day, it expires. Simple.
Now, you can extend those 60 days at any immigration for a further 30 days at a cost of 1900 THB. Same as before, the moment you leave, it expires as it's just an extension of your SINGLE entry tourist visa.
Now you could get a re-entry permit but that doesn't make sense on a tourist visa. You will not get more days. Just exit the country and come back and get an other 30 days.