LBJ posted yet another shirtless workout vid Friday morning ... vibin' out to Meek Mill's new "Wins & Losses" album. This time, the King raps, sings and even maniacally laughs at his haters.

LeBron's been mocked by pretty much the entire Internet -- including Steph Curry -- for his first viral gym sesh, so it's only a matter of time before your timeline gets flooded with new challenge vids.

At one point, LBJ makes sure to point out one of Meek's lyrics directed at the President -- "Trump ain't feelin' us" ... which makes sense, considering Bron's never hidden his feelings towards POTUS.

As for LeBron's singing ... it's never too late for lessons, bro.