Muay Thai is not good for bodybuilding. If your goal is to put on as much muscle mass as possible, then Muay Thai gym will take away from that process. Especially at the intensity of many Muay Thai training sessions and the volume of Muay Thai conditioning that you need to do to be fight-ready.

Can Muay Thai get you in shape?
 
Providing both aerobic and anaerobic workouts, dedicating 60 to 90 minutes on Muay Thai training can give you 1,000 to 1,200 calories burned in one session. This explains why Muay Thai is a perfect way to get rid of stubborn fat and tone your muscles while improving flexibility and having a stronger core.