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Of course, some will not do well in the labor market, but would they do better here? You seem to suggest they are working as singles instead of in a couple. I know many that are doing quite well. One with a 4th-grade Thai education, started at $11 an hr. doing landscape, but being a very hard worker was making $24 an hr in less than 4 years. Another got a job driving mail delivery for the US post office with all the benefits. You really have a very negative opinion of Thai women.
As for the US marriage. As a US citizen, you are not allowed to have more than one spouse. If you have a wife in the US and you get a legal marriage here or in any other country, you can be prosecuted for bigamy.