Matched by need
A training holiday is a legitimate goal and some camps are genuinely built for it. The failure mode is booking a serious camp and feeling guilty for going to the beach, or booking a resort and getting no real coaching.
If you are bringing someone who is not training, the location matters more than the camp. An excellent camp in a boring town is a bad holiday.
2 camps
Ao Nang, Krabi / Small camp
One of the few established camps in Krabi, which is the appeal: mainland scenery and climbing on the doorstep without the density of the Phuket scene. Smaller trainee pool means fewer partners at your exact level.
Pattaya, Pattaya / Mid-size camp
Runs structured multi-week training and weight-loss camps as packaged programmes rather than open drop-in training. Suits people who want the schedule decided for them.
Wrong customer
These are not bad camps. They are camps where you would be the wrong customer, which is a different and more useful thing to know.
Chalong, Phuket / Mid-size camp
MMA-first gym rather than a Muay Thai camp that added MMA. The right pick if mixed martial arts is the actual goal and Muay Thai is one component of it. A poor pick if you want a traditional Thai Muay Thai experience.
Bangkok, Bangkok / Mid-size camp
A Bangkok gym with a real stable of professional Thai fighters rather than a foreigner-first operation. Training alongside working pros is the draw. Expect to be the weakest person in the room for a while, which is the point.
Bangkok, Bangkok / Mid-size camp
Attached to one of the most significant promoters and stables in Thai Muay Thai. The pedigree is the reason to go. Not designed as a soft landing for a first-time trainee.