His dad was even HAPPIER -- because Dennis Graham had $100,000 riding on the Raps ... AND WON!!!

"I am the happiest guy in the world," Dennis told us in Hollywood with 2 ladies on his arms.

"I bet $100,000 on the game and I won $300,000!!!"

You see this? Drake's dad is RICH!!! (Okay, *more rich). PIMP HATS AND CHAINS FOR EVERYBODY!!!

There's more ... Dennis also has some advice for the Raptors when it comes to visiting Donald Trump -- DON'T. He thinks the team should meet with Canadian Prime Minister Justin Trudeau instead.

"Justin Trudeau is a much classier guy than that IDIOT Donald Trump," Dennis says.

Oh, and Dennis also explains why he wasn't at the Raptors victory parade in Toronto -- telling us he's got big things in the works in Hollywood that took priority.