Cardi B Twerking Poolside Amid Las Vegas Police Battery Investigation

Cardi B ain't sweatin' the Vegas cops ... 'cause she was dancing her butt off poolside the same day she was named a suspect in her microphone-tossing case.

Cardi posted a video Monday, which shows her and hubby, Offset, havin' a grand ol' time on the rooftop of what appears to be a Vegas hotel.

Both rappers are in bathing suits going absolutely bonkers -- Cardi is twerking like crazy in the pool as Offset wildly dances around her.

The two could not seem happier ... her police troubles seem to be the last thing on their minds.

Cardi was named as the suspect in a battery case after she hurled a mic into the crowd at her Vegas concert Saturday, hitting two people.

Video captured the moment someone splashed Cardi with a drink while she was onstage at Drai's Nightclub ... after she encouraged the audience to cool her off with water in the extreme heat.

Cardi clearly didn't approve of the way the liquid drenched her body, prompting her to throw the mic, which first struck the drink thrower and then ricocheted and hit a woman standing nearby.