Country Singer Ernest Falls Off Stage Opening For Morgan Wallen

Morgan Wallen's opener followed in his footsteps with an onstage fall this week -- but this one went off the rails ... or into the rails, more like.

Country singer Ernest was performing before the main act Thursday in St. Louis when the stumble happened, and based on video TMZ obtained ... you can see just how out of nowhere it really was.

Watch ... the guy's signing autographs for people in the front row, and follows that up by throwing roses out into the crowd. It was one too many, though, 'cause the dude ate s***.

As you can see, the force with which he chucked the flower launched his body forward ... and Ernest actually went over the edge of the stage right into the barricade below.

He posted BTS footage after the fact, and you can see it was kinda ugly. He got pretty tangled up there for a sec -- but surprisingly, he popped right back up and looked fine.

All's well that ends well ... which was reflected in the comments he received from Morgan himself. MW wrote, "Stuck the landing" -- and other artists got in on the ribbing as well, including Nelly and Dierks Bentley ... who were all amused by the stunt.