G,
It really depends on your priorities.
So far I've trained at these gyms:
http://www.rawaimuaythai.com
http://www.kittanamuaythai.com
http://www.thailandmuaythai.com
I'm currently at the last one - Phromthep Muay Thai.
This camp is everything that I personally want in a camp. There is a strong focus on nutrition and an on-site restaurant with reasonable prices and a wide range of very healthy food that will get me back into shape and have me performing at an optimal level. I am not trying to become a world class fighter and many other people here came for the same purpose - get fit.
What are your priorities? In which city do you want to train?
A couple things I dislike about Phuket are that taxis are a ripoff and the prices for everything tend to be jacked up. However, the WIFI at this camp is phenomenal, it's got everything I could possibly need on site, and it is a quiet place for me to get fit and launch my products over the next couple of months.
Two friends of mine will be opening a gym in Chiang Mai which will have all of the things that Phromthep is currently offering me. However, the prices will be significantly lower at around 17,000 baht a month for housing and training - whereas I am paying 27K baht a month in Phromthep for housing and training. I'm wiling to accept this steep cost in Phuket at the moment because there is no other camp in Thailand, as far as I'm concerned, which has such a solid focus on nutrition. I'm getting a body composition test from an on-site trainer tomorrow and will be tracking my progress with time. As far as I know, there is no other place that serves my specific needs to this degree.
The last place where I trained, Kittana, was highly unstructured. This was good in some ways and bad in some ways - but I tend to benefit more from a structured training environment - at least as far as a muay thai class goes. I would not respond well to someone barking orders at me while I lift weights.
After at least two months here I will probably go and start training and living at my friends' new gym in Chiang Mai. I'll keep you guys posted on how things are developing but, given the partners involved in the venture, I am very confident that they will create a world class gym here that will provide everything you could need.