It's pretty funny ... Morgan was doing his thing at U.S. Bank Stadium in Minneapolis when all of a sudden a blue thong comes flying towards him, landing on his face -- with a little coverage from his hat.

The panties carom off Morgan's dome and then he catches them with one hand like Randy Moss before finishing the lyric like nothing happened. We'll admit ... it's all pretty smooth.

Unfazed, Morgan turns and flicks the panties to the crowd on the opposite side of the stage as he dances away ... and it all happens super fast -- almost like this wasn't his first panty rodeo (and we're sure it wasn't).

We've seen lots of stuff being thrown on stages recently ... but this one seems pretty harmless.

Bebe Rexha certainly had it worse ... she took a phone to the face last June, and the guy who allegedly threw it at her got arrested.

Morgan's more on the Drake side of things ... remember when women were throwing bras at Champagne Papi during his last tour?!? Funny enough, the two of them linked up late last year -- so now, they got something else in common.