Anonymous participant You do not know if it is legit. It might be a legit Muay Thai school, but never did the paper work to help getting a DTV. The school as to register itself at some government authority. Most likely the Ministry of Education. Just like for an ED visa. If they never did that, making you a contract, is not the valid requirement for an DTV visa.
You an not just go to a random school, buy a half year contract, and get a DTV visa with that.
If you like to Chiang Mai, I can recommend two schools. And one on Phuket.
Anonymous participant 563 You forgot the meditations. The prayers. No smoking. No Beer. No sex - not even looking at girls. And the random wake ups at night with water buckets full of ice cubes.
And honestly: the rice is not the rice we used to have. It is full with dead bugs of various kinds.
Then there are the guards that let you in and out ... if they let you out ... which you have to bribe every time.
But as you said: with a little bit of focus and determination, easy peasy!