Shaquille O'Neal is weighing in on Ja Morant's controversial gun-flashing Instagram Live session ... telling the Memphis Grizzlies star he has to be smarter moving forward -- saying, "You're not a rapper, you're an NBA player!"
Shaq conveyed his memo to the 2-time All-Star during NBA on TNT on Tuesday ... saying Morant put himself in his current position with the NBA, Grizzlies, and fans as he chose to push the IG Live button and brandish a gun.
"You don't go live, nobody knows he has a weapon, [then] we're not talking about this, but HE did that," the 51-year-old said.