Muay Thai has nothing to do with it. 100% genetics. Calves have always been 100% genetics and will always be. Nobody except for Arnold has ever provided evidence for having brought up their calves without it being blatantly oil. Yet every fucking schmuck has his theories about how to do it. Asians have the best calves. If your calves suck you should find another hobby, consider ping pong or curling, because nothing you ever do will make up for your pathetic calves and random Asians and fat people will mog you. Being huge will only make your embarrassment greater.
Pic related, this is what peak human genetics look like. If your calves suck, just give up and take up stamp collecting.