Of course they know where he is, out of their jurisdiction is where.
Sure this guy definitely needs to experience prison love if guilty but there is no Thai Batman (sadly) to go get him.
That scene where they sky-hook the villain, transport him back Stateside, and leave him tied up with a note out front of the police HQ. "Your're friendly neighbourhood Batman"
Not going to happen, fun if it did, but nope.
The thing is even if they got him, charged/prosecuted/guilty there is no way a Thai billionaire's heir apparent is going to do jail time. This kid is not lying awake at night thinking about the life he took.
Can you imagine the family lawyers, yes you killed him (they would be under strict orders not to say it that way though, it hurts his feelings), but do this and it will eventually go away.
His mum holding him to her bosom, stroking his head, it's okay, he was a pooouurr.
He got away with it, good chance that when he is older he will hunt humans for sport somewhere.