You can do as you wish. You paid for those classes as did loads of people so the Muay Thai School and Thai Govt did well out of it. The classes are probably overbooked so they won't miss you for 3 months.
Milk and people. On that note, about men especially single men, I think that ironically single men will spend more because they're looking for amusement or out drinking with buddies. If they joined a gym, they'd save money, health costs and probably meet someone.