The first reports I saw said he was picked up in Thailand for sex charges there first, but looking into it further I see that Thai officials said he didn't have any pending charges there. It could be that the initial reports were just completely false and made up out of thin air and he wasn't in trouble or under investigation for anything in Thailand, or it could be that he did get arrested in Thailand but they did not end up filing charges because he was going to be deported. Regardless, I'm just not so sure this guy killed the girl. He might have, but I'm thinking there is a pretty good chance he's just a nut or he was trying to get out of something in Thailand, or both. Several people have already "confessed" to this killing. That is not uncommon in famous cases. Nuts will say they did it, prisoners trying to get out of prison will lie and claim their cell-mate admitted to the killing and offer to testify in exchange for a deal. You have to be cautious about believing these claims without some strong corroborating evidence.
This is not the guy. He wasn't in Boulder in December 1996.
The original statement, IIRC, was that he had been arrested in Thailand on unrelated charges. Those unrelated charges were apparently the California charges. Thailand immediately clarified that he had not been charged with any offense in Thailand.