Can I apply for a single re-entry permit for each trip out of Thailand, or should I get a multiple re-entry permit?

I entered Thailand with a 90 day Business Visa last week and I will apply for a re-entry permit at Don Mueang Airport when I fly out for a short trip to Malaysia on Thursday.

At this stage I'm not sure if I will depart Thailand more than twice during the next 90 days so it would be cheaper just to apply for a single re-entry visa each time rather than the multiple re-entry visa.

Does anyone know if this works? Can I get a single entry visa this week and then another the second time I leave the country? Or should I pay the extra fee and apply for a multi-entry just to be sure.