Soulja Boy is 23 years old and has more money in his sweat pants than you'll see in a year ... which he happily showed off to our pretty jealous photog.
Soulja was strollin' around in LA Saturday when our camera guy asked if he was still celebrating his bday (it was July 28) -- at which point Soulja went all Chief Keef on him and flashed some bills.
By "some" bills -- we mean STACKS and STACKS and STACKS of cash. Possibly more than Keef.
As for why he walks around so pocket-heavy -- we'll let him explain. It sort of makes sense.