Chris Brown jacked a fan's hat during a concert ... at least according to the fan who now wants more than $2,000 for his troubles.

According to the lawsuit filed by Marq Stevenson ... he went to CB's Dallas concert last year, and passed his cap to one of Brown's lackeys to get the singer to autograph it.

Stevenson says he did NOT get Brown's John Hancock, and did NOT even get his cap back. In the suit, he says he DID get bullied by Brown's crew.

He now says the hat was stolen, and wants compensation for the $25 lid. But that's not all -- he also wants $225 for his floor seat ticket, plus $2,500 for the bullying. Yes, that's $2,750 ... for a hat.

Stevenson is no longer demanding an autograph.

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