[Lindsay Lohan] has become a regular at a downtown dive, partying into the wee hours with drunken pals. Last Monday, LiLo hit Sing Sing Karaoke bar with a gaggle of girlfriends on Avenue A in the East Village, where she proceeded to start a verbal fight and refused to leave at closing, planting herself at the bar until almost 6 a.m., multiple sources tell Confidenti@l.

"Lindsay was chain-smoking," our tipster says. "She walked in sober and she left looking tired." The night took a turn for the worse when a customer overheard LiLo get into a "disturbance" with a staffer, as she begged to keep the bar open past closing and was acting "insanely belligerent."

When asked to leave, Lohan called the cops, claiming staffers had locked her in the private karaoke room. The NYPD showed up, but no one bothered to file a report. When Lohan and the group finally left, staffers found their private karaoke room littered with trash and empty bottles.