I would HJ, I wouldn't have a sex tourist as a friend, no matter how 'lovely' a friend he appeared.
Perhaps because I can spot seedy myself and wouldn't have it anywhere near me or my family.
You say your friend who went to Thailand and paid women to fuck him, is feeding you a cock and bull pile of shite about it being decent and not seedy at all (if he has to say it, it's over justification and trust me it's not OK)
He literally didn't give a fuck if the woman was pimped or not, he got his rocks off and is spewing a pile of lies to you to justify it.
If you choose to swallow it, more fool you.
You can tell a lot about a person by the company she keeps. Another one? If you lie down with dogs, you are going to get fleas.
A man that has to pay for people to fuck him is not a good person. A person who travels to a poor country to pay someone to fuck him is called a sex tourist, and is NOT a good person, he is a person to avoid. Like the plague.
Carry on defending him, as is your right, doesn't make him, or you look any better for it.
I feel for you, I really do, your sense of loyalty is amazing, but it will not do you any favours at all long term.