Betting in chess sound as a nice way to gamble, the problem is people could use a computer in the hard level to play chess against other people, that way the gamewill be rigged and the winner will be the one with a smarter PC.
So, if you find a place to bet on chess, i would like to recommend you to not place a bet.
I can imagine of that.
But there could be some ways to know that your opponent is the one actually playing it. In that manner, you'll be able to verify that there's no one cheating on the match.
Or, there are platforms and software that would definitely be for the sake of the PvP so that no one uses an AI that nobody knows that he's been cheated on.