Ne-Yo Simulates Sex Act on Stage During 'Nights Like This' Tour on Video

Ne-Yo got down and dirty on stage during his "Nights Like This Tour" Friday night in Las Vegas ... simulating a sex act while floating above the stage with his dancer.

Check out the eye-popping clip -- a dancer in barely-there BDSM-style lingerie walks up to him on stage as he attaches himself to a mechanism to lift him above the stage. She hops on him, and they seductively twirl into the air together, and she eventually does a split across his chest.

It gets dirtier from there -- near the end of the video, Ne-Yo lifts the performer to his chest and dives his head in between her legs ... simulating oral sex while they continue to float above the stage at the MGM Grand Garden Arena.

And to make things more interesting ... he did the sexy move in front of his mom! That's right -- at another point in the concert, the "So Sick" hitmaker dropped the mic and later explained the mishap occured because he's super nervous with his mother in the crowd.

Ne-Yo is currently on the U.S. leg of his and Akon's joint tour, which kicked off in April in Dublin, Ireland. They've got a week left ... wrapping up in California next week.