Viet Nam is cheaper, plus you may visit their excellent museums where they will proudly tell you how they won the war, which they did. But you will need to accept you are living in a communist country (shock horror)
Thailand has had uncontrolled development in tourist areas eg they killed the goose, plus they make visa's very hard..

Horrible heat & humidity! No thanks!

Costa Rica or Panama is closer to home where medical care might be a concern. And they are a democracy, mostly where as Thailand is a military government after the coup. Retirement costs? Plan early & invest more than one already is. Diversify with dividend paying stocks, emerging markets,, Savings bonds, Certificate of Deposits as performance dictates at the time. Be consistent & have a plan that is flexible as times change. SSI was never meant as a retirement plan. It was only intended for food, that Americans didn't starve during the Depression & beyond. We are responsible for our retirement. Not the government.