I been thinking about Thailand for retirement. You can live like a rich man on what I get in retirement. I been reading about it for years and thinking about it. There are some problems with it. One is the very high cost to fly there. I don't think I would ever have any family drop in for a visit if I moved there.
I have heard a lot of good thing about Costa Rica. I don't think it is as cheap as Thailand however. This one site says you can live in Costa Rica on $1000 to $1300 a month.
Here is a site with a little information. The site is selling a book on the subject.
