can an U.S. citizen buy a house in a country like Thailand for around 1/10 the price of one in the USA? why or not?

A US citizen can't buy land in Thailand. No foreigner can. They could buy a condo. Why is it like that? Because that's the way Thailand wants it. I'm not going to check how it is in all the other countries 'like Thailand', whatever they are.

The prices are cheaper in Thailand than in the US because it is a poorer country. People don't earn as much so they can't pay as much.

No you can only buy a condo.

But most people just rent places.

Or get a wife to sign it.

Foreigners can not purchase land to build a house in Thailand.  The best you can do is build one on the land of a Thai person, but you will not own it.  See a lawyer for more options but you still can not own it.

If the country doesn't have laws against it; sure. (Some countries don't allow foreign citizens to buy land/property)

But they won't be able to live in it without a visa. 

A one room flat is about $20,000. In Russia, a two-room is $15-20K. Labor is cheaper. (ever wonder why "made in China" is so popular? Factory workers get about $200 a month in China. $500 a month in Russia. $2000 a month in USA. Thai bricks are made with Thai labor. Thai cement is made with Thai labor. Wood and steel are likely imported into Thailand from, CHINA!! Cheap Chinese Steel and wood building materials. That is why it is 1/10th price of USA. 

There was a two or three story house for sale here in Russia, 4000 sq ft, detached heated pool, detached garage, "banya"- a Russian "sauna", 9000 sq ft yard/garden, fenced in by brick, $140,000.