Bobby Brown -- Back to Life at Karaoke Night ... No Talk of Bobbi Kristina

Bobby Brown is finally getting back to normal life -- in fact, so normal that hours after flying from Atlanta to L.A. ... he got on stage for karaoke night at a pizzeria in the Valley.

Bobby was at Paoli's Pizzeria and Piano Bar in Woodland Hills, CA on Friday night. Sources in the bar tell us it looked like he was having a guys' night out -- with about 7 or 8 friends -- from 9 PM until about midnight.

We're told one patron attempted to talk to him about Bobbi Kristina's condition -- but Brown politely replied, "I don't wanna talk about that."

TMZ broke the story ... Brown left his daughter's bedside Friday for the first time since she was hospitalized. We knew he was performing at the Soul Food Festival in L.A. on Saturday night, but a karaoke event ... we did NOT see coming.