Of course while owning a villa in Koh Samui in very desirable, business in Thailand is not always straightforward. There is legislation that can make it tricky for foreign nationals to own land in Thailand. Oddly owning the villa itself is no problem, but the land is slightly different. It is possible to lease land, and this is usually a 30 years lease. This can be renewable for up to 90 years, but this is a little trickier to organise. While saying this there are many people, in fact it would be fair to say most foreigners effectively own their land and property in Thailand.
The laws here may seem restrictive and the political climate can seem odd to an outsider, but fundamentally Thailand is a very stable country, and has never really experienced huge political upheaval – despite the recent coup for instance the only differences tend to be political posturing, and unlike it's neighbours Thailand has remained stable for many years.
A key factor to bear in mind when thinking about Thailand is that it has always been aware, unlike surrounding countries, that it has a certain reliance on foreign investment – just look at the city of Bangkok to understand how Thailand feels about foreign influence and investment. So while many of the laws in Thailand seem to be prohibitive to foreign investment, you will find that with the correct people to advise you, that the reality is that there is nothing to prevent you owning your dream home in Koh Samui.