Pauly D to Khloe: Give Tristan Thompson 2nd Chance!

Pauly D is calling for MERCY for Tristan Thompson ... saying Khloe Kardashian should give the dude a second chance after getting caught cheating on her during her pregnancy.

"OHHHHH," Pauly told us while outside 1 OAK in Hollywood ... "He got caught up there!"

He certainly did ... footage of Tristan motorboating, kissing and messin' around with other women (not named Khloe) surfaced this week as Khloe is getting ready to give birth to their kid.

Still, Pauly says he hopes Tristan gets another shot to be the faithful baby daddy Khloe wants.