It all seems a bit silly to buy thai property as an investment - why not buy in your home country? You can still live in Thailand if you want to but you have much more rights and, if you are clever, less tax obligations.
It is also much cheaper to rent than buy here.
I wonder if the only reason why farangs buy property here is because their thai waives nag them into it as an insurance policy for themselves (by having the property in their name). It seems the only logical answer to me.