Want to retire in SE Asia, 36M US Citizen, how should I plan?

A few years ago I was speaking with a customer service rep for my wireless service, and we got to talking about affordability while we was waiting for my phone to be activated. He was based in Cambodia, and mentioned that there were many US expats in the area. Based on what he shared, one could live very comfortably for a fraction of what it would cost in the US.

Given the current state of affairs in the US, both political and economic, I am seriously considering retiring abroad. Combined with the amount of retirement savings I expect to have in 30 years, the lifestyle I would like to live, and the climate I would like to live in, southeast Asia seems very attractive.

My biggest concerns are political instability and the quality of medical care. I have a decent understanding of geopolitics, but I'm no expert on SE Asia.

Which nations provide the best balance between stability, availability of medical care, and affordability?

What else should a Westerner consider regarding emigration to SE Asia?

Politically I'm fairly liberal, and definitely not a stereotypical ignorant American. Still, I expect there are at least some places that are less than accepting of westerners and/or US citizens. I have no issues assimilating into the local culture; which countries or regions would make this the least difficult?

Finally, I'd like to understand the perspective of people living in Southeast Asia regarding Western emmigration. Do you believe this helps local economies by bringing foreign investment, or do you believe it causes harm through gentrification or other means?