If you are interested in health holidays, massage, yoga, detox, spiritual awakening and even hypnotherapy Phuket is a great place to visit.

Phuket is actually the same size as Singapore, with a large ex-pat community, decent hospitals, spas and retreats.   The ex-pats seem to mix well with the Thais, even in business.  

There are some wonderfully spa health retreats.  SixSenses, Evason Resort, in Rawai is simply wonderful, and their spa menu is amazing, they have a great restaurant and juice bar, fantastic views over Phuket and you really come away feeling so much better.  It's not cheap - but worth every penny.   What's more you don't actually have to stay their to use their spa.  Infact, most of the best spas are linked to resorts, but you don't need to be a guest to benefit from the facilities.   In the north of the island, Twinpalms Phuket Resort has a great spa - Palm Spa, you could also try the Residence, near to Bang Tao beach.