hi, not 100% sure of your exact definition of a "purpose built retirement village". If you mean simply a cluster of independant living units (i.e. no hostel or nursing home level care) then I think you will find something. Have you tried google searching already?
I saw one development under construction a few years ago - can't recall the name of the place. I was with Larry Cunningham, the Australian Honorary Consul in Phuket, a guy who is very well briefed about real estate there. If you can't find anything on the net then perhaps you could google his name and then send him an email.