Shareef O'Neal isn't just a stud basketball player -- he's also got some reporting chops ... and he's got the inside scoop on LaMelo Ball. Shaq's son was at the TDE Watts Christmas Charity Concert when he told us he spoke with LaMelo about his move to play pro ball in Lithuania ... and told us how the youngest Ball bro REALLY feels behind the scenes. We also told Shareef about the NEW hoops league LaVar Ball is trying to launch -- and asked if he would ever consider joining up with his friends.