Brown -- who's friends with Kehlani's NBA star ex-boyfriend Kyrie Irving -- went off on Kehlani in the middle of the night saying, "There is no attempting suicide. Stop flexing for the gram. Doing sh*t for sympathy so them comments under your pics don't look so bad."
As we previously reported, Kehlani was placed on a psychiatric hold Monday after posing a threat to herself in the wake of rumors she cheated on Irving with a previous boyfriend.
For the record, Kehlani strongly DENIES cheating -- saying she and Irving were broken up when she got back with her ex.
But Brown ain't buyin' it -- trashing Kehlani in several tweets ... and saying she's basically been blackballed from NBA games.
The Internet went insane over Brown's comments -- with people coming out of the woodwork to blast the singer for being insensitive.
Brown responded by saying, "I'll be the BIGGEST PIECE OF 💩. But ima ride for my Homies regardless. KYRIE is probably one of the only good guys left. IDGAF!!!"
As for Kehlani, it's unclear if she's in the hospital -- but sources close to the singer tell us she's doing much better.