Update, I saw him yesterday and he showed me some evidence of funds deposited to his account on Saturday evening, he claimed he saved 1/2 of his tips as against 4/6 that were agreed(I can't tell because I don't know the actual total). But the good thing and what impressed me was his determination to get better and giving the strategy a try. He thanked me very much and I bought him a bottle of chilled beer tho celebrate his little success. I hope he continues and doesn't relent.

Thank you all for your suggestions, I showed him some comments from this thread so he'll see for himself that he started off his employee's activities on the wrong foot.
He still argued that if he doesn't gamble, he wouldn't be able to entertain his clients well and give them meaningful suggestions from his experience that brings about some of his tips.

Good thing is that he's starting to take things easy, I didn't ask him to stop gambling entirely because I know from experience he'll not agree easily, he's changing and that's more important.