I gave him? the benefit of the doubt

[Andail]

Then this big guy come in and bets heavily and my friend has a hand that can't possibly lose, so this guy calling himself 'Uncle' convinces my friend that they're playing this big guy for a fool and that my friend should go back and get the money needed to call the big guy's hand.

This doesn't sound like Blackjack really, but anyways, good thing he went away

[Stupot]

Then this big guy come in and bets heavily and my friend has a hand that can't possibly lose, so this guy calling himself 'Uncle' convinces my friend that they're playing this big guy for a fool and that my friend should go back and get the money needed to call the big guy's hand.

This doesn't sound like Blackjack really, but anyways, good thing he went away

That's because I said 'call' which is more of a poker term. It was definitely blackjack, though. And I've found a webpage full of people saying they've fallen for exactly the same thing:
http://www.bangkokscams.com/scams-in-bangkok/blackjack-scam.html