Play video content EXCLUSIVE TMZSports.com

Good news for the UFC ... its biggest star is finally "getting his head straight" ... and a former WWE superstar is looking like an "absolute stud" during his transition into MMA ... so says Dana White.

First, Jon Jones ... he's essentially been off the grid since his April arrest for hit and run in New Mexico -- an incident where cops say they found weed in Jon's car.

But when we saw Dana White at a UFC/Reebok event NYC moments ago, the UFC honcho told us he's quietly doing all the right things to get his life back in order in and out of the octagon.

As for C.M. Punk ... the ex-WWE superstar is "looking phenomenal" during his training. White says he's a beast in the making. Stay tuned on that one ...

White also had some advice for Ken Shamrock ... RETIRE!!!!

"Ken you're 53. Time to hang it up."