I have a house down your way but also have a property up in Chiang Rai. My name is registered with immigration on both properties so never report moving between the two. I also do my yearly extension in Chiang Rai as its easier but the IO has no problem having two addresses or ever my 90 day report.
There loads of these tantric workshops on Koh Phangan. The most interesting in my humble opinion is called the all woman only Jade temple. They sell jade round balls to be inserted into the so called female Yoni they also advertise Yoni massage workshops Google. It would be an interesting fly on the wall experience .
I can vouch the islands of Samui, Phangan and Tao especially the latter two are the Wild West . Anybody that lives or knows the last two islands people work, crime etc and basically do as they like. Send a crack team there and clean up the islands please.