Is there any age limit for learning Thai boxing?

There is no age limit for this, the key is whether to pay tuition or not.

Moreover, there is a lack of formal Thai boxing halls in China, which are generally found in first-tier and second-tier cities.

It's basically amateur muay Thai. If it is professional Muay Thai, you will not retire after 40.

With money, the economic situation varies from place to place, and some are 11 thousand months.