Shia LaBeouf in His Underwear in Italian Hotel Lobby, Begging for a Light

Topless Shia LaBeouf's putting his own twist on "When in Rome" ... appearing to cause some commotion in a hotel lobby over there, and we have the video.

Oh boy ... so, as you can see, Shia is wearing only his boxer briefs with a loose cigarette hanging from his mouth.

A woman, who looks slightly embarrassed, walks away as Shia begs, "C'mon, bro ... give me a f***ing match. You got a match?"

As we reported ... Shia traveled to Italy to attend his dad's baptism. Court docs show his request to leave New Orleans was initially denied in favor of him continuing his substance abuse treatment. But later, his lawyer came back with a new request, which the court greenlit.

His legal mess stems from a rough Mardi Gras morning in February, when the former Disney star got into a bar brawl, ended up on the ground during the fight, and was arrested. He was picked up again Feb 28 on an additional battery charge tied to the same incident.