John Salley -- BIG BOOTY PATROL ... in Beverly Hills

You know what makes John Salley happy?? A GREAT BADONK ... and last night in Bev Hills, the former NBA star was a very happy man.

TMZ Sports was talkin' with Mr. Salley outside Mr. Chow when he stopped the conversation dead in its tracks -- to focus our attention on a gigantic booty that was shuffling our way.

John smiled ... traded some high fives with our photog ... and then dropped this nugget: "Ya never stop being an athlete."