Play video content EXCLUSIVE 4/20/18 TMZ.com

Belly was the recipient of several flying fists from security guards during The Weeknd's performance at Coachella ... even though the rapper performed at the fest earlier in the night.

Belly -- who actually has a hit song with The Weeknd -- was in a line of people walking from the sound booth to the VIP area near the main stage while The Weeknd was singing "The Hills" ... according to witnesses.

For whatever reason, about 10 men who appear to be Coachella security staff start PUMMELING Belly ... and don't let up for several seconds. The video's wild.

no negative bullshit can steal my joy.. I performed the best show of my life, on 4/20 at Coachella ‼️I really came from nothing, and I’m still here.. it’s gotta mean something. @reBELLYus

Belly isn't letting it get him down, though. He just tweeted, "No negative bulls**t can steal my joy" and added earlier ... "I'm great y'all. I love you." He also got a shot in at the guards who went after him, saying ... "20 of you p***ies couldn't take me off my feet."

We're told police were not involved in the incident -- by the time they showed up everyone had dispersed and no report was taken.