"The goal is to play for a NBA team, not a southeast Asia or Euro team."
Have you spoken to him? I don't know what his goal is. Regardless, he will almost assuredly be drafted, and be on an NBA roster this year.
"I think he would prefer to live in the US for 1 more year, make 1st round money, and remain in the US to play in the NBA where he can possibly win a championship."
Well, then you're clearly wrong, because either:
a) He will be a first rounder
b) He would not prefer to wait and be a first-rounder (I guarantee you he know more about his draft prospects than you do)
c) He feels like his height is a prohibitor from him EVER being a first rounder, so he may as well go now
d) He figures that regardless of where he is drafted, if he's good enough, he will play. This is almost assuredly true.
Further, your comment was that "it's not much money unless he's a first rounder". Making over six figures is, to most people, a pretty solid amount of money. Is it Lebron money? No.