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(TMZ) - Chief Keef is done being a pot-smoking reckless driver who carries around tons of cash ... at least that's what he says, according to TMZ.

Keef was cruising out of LAX Saturday night - and heading to an undisclosed rehab facility - when he told TMZ about the big life changes he's making.

As TMZ previously reported ... a judge ordered Chief to rehab after he failed 3 random drug tests while on probation stemming from his speeding case.

C.K. clearly wants it to be known he's making changes ... but with Keef constantly flaunting his weed habit on Instagram ... and 3 positive drug tests for marijuana - TMZ had to ask ...