LeBron James Says Playing With Son Would Be Top NBA Achievement

Not one, not two, not three ... not even a bunch more championships would make LeBron James as happy as playing with his son in the NBA -- so says the King himself.

James' company, UNINTERRUPTED, released some behind-the-scenes footage from the lead-up to the NBA Finals ... when LeBron shockingly told reporters that playing with -- or even against -- LeBron James Jr. in the league would be his crowning NBA moment.

"You want to ask me what was the greatest achievement of my life? If I'm on the same court as my son in the NBA," James said.

"That would be no. 1 in my lifetime as an NBA player."

FYI ... Bronny's currently a 13-year-old eighth grader ... which would mean LeBron -- who turned 33 in December -- would have to play another six years in the league AT LEAST to have the shot to hoop with his kid.

BUT ... judging by Bronny's skills already -- a 39-year-old LeBron might just get his wish.