your question is answered in the article you cited: he entered Thailand on April 16 but the warrant in Georgia was issued on May 10; so he was not yet a wanted felon.
find a Thai person who is willing to report him anonymously to immigration for having illegal workers. You should stay out of it personally. maybe best to simply walk away
whatever works... it is likely the cause of his being turned away at the airport ; I know several people in the States who has the same problem- I was flying once from Taiwan and the airline wouldnt sell me a one way ticket- I had to go to the Thai consulate and explain to them that I was headed for Cambodia by land and they wrote a special note to the airline for me.
have him buy any cheap air asia ticket out of Thailand for sometime before the visa expires- he can throw it away or use it - probably no return ticket is the reason