The singer appeared intoxicated Thursday night outside The Fleur Room in West Hollywood, and April certainly thought he was ... as she put it, "his bitch ass is so drunk."

The video picks up with Robin trying to grab a bag from April outside the club entrance, but she breaks away from him and hails a ride ... and then he stumbles on his way back into the club, falling into a bush.

April calls him out for being wasted, and says he's embarrassing them with his behavior ... telling the bouncer to not let him back inside.

Robin continues trying to get his hands on April's phone, for some reason, and they get into a physical struggle on the sidewalk as she pleads for him to quit.

Eventually, a black SUV pulls up and Robin holds April in a bear hug from behind as she struggles to get to the car. Robin is smiling and laughing the whole time, but April's clearly not amused as they finally climb into the vehicle.