Joe Jackson -- 83-Year-Old Hits Vegas Club ... at 2 PM

83-year-old Joe Jackson threw on his best track jacket ... and goldest chain ... and hit the club scene in Vegas this weekend ... at 2 IN THE AFTERNOON.

Michael Jackson's father was chillin' at Lavo Champagne Brunch at the Palazzo Hotel ... a full-on nightclub-style party scene ... that serves almond crusted French toast.

Sources at the club tell TMZ ... JJ arrived with a male friend ... and wasn't boozing, only drinking water.

But he WAS pimpin' it ... hangin' out at a table with a group of hot chicks. At one point, he handed his camera to someone and said, "I want a picture with the girls."

After the pic, the girls described JJ as a "sweet old man."