Dennis Rodman -- STRIPPER FIESTA ... At Thong'd Out BDay Party

Ass. Ass. Ass. Ass. Ass.

That seemed to be the theme at Dennis Rodman's birthday party blowout this weekend ... and TMZ Sports has all the thong'd out footage.

It all went down at Sapphire gentlemen's club in Vegas -- where The Worm was constantly flanked by a team of talented twerkaholic strippers.

But it wasn't just about lap dances ... Dennis also mingled with fans, signed autographs and took pics with anyone who asked.