Chief Keef -- Thumbing His Nose at Obamacare ... Says Baby Mama

Barack Obama would be SUPER DISAPPOINTED in Chief Keef ... 'cause according to his baby mama, the rapper has FAILED to get his daughter health insurance.

It ain't like Chief can't afford it ... as his ex points out in legal docs, he signed a $6 million record deal in 2013 and has at least $594,167.46 in liquid assets.

The woman, Jasmine Woodford, claims she's just a poor nursing student who can't afford to buy a health plan herself ... and a judge previously ordered Keef to pony up, but he never did.