Chief Keef NOT Lovin' It ... Rejected By McDonald's

6/29/2013 12:45 AM PDT

You're rap protégé Chief Keef ... you're making buckets of money ... and all you want is some delicious McDonald's grub ... easy right? THINK AGAIN.

TMZ obtained hilarious video -- courtesy of -- of Chief and a buddy driving through a McD's this past week in Illinois ... after ordering almost $50 worth of food. Food you can ALMOST taste. 

Problem is ... when Chief goes to pay he runs into a major -- and pretty rare -- monetary problem. It's definitely not what you think.

Unless you're thinking of making it rain with hundos. Then it's exactly what you think.

FYI: no one was arrested while making this tape. Probably.