As I quite like the idea myself to spend some considerable time in Phuket and will do so once my house in the UK is sold and that soon I hope if the estate agent gets a move on! And hell, I can work from anywhere so why not from there...oooops, as long as ADSL works of course. So I had a quick look at the insurance issue. It appears there are a number of Insurers that will provide cover for "long-term-ers" of up to 18 months.....that may be enough to find an alternative after....here is one of the links.....
http://staysure.co.uk/travelinsurance/longstay.php