CM Punk -- UFC 170 Hangout Was Just For Fun ... Says Dana White

CM Punk's first public outing since walking away from the WWE last month was Saturday night in Las Vegas at UFC 170 ... and even though he was sitting ringside with the company's head honcho -- Dana White says they didn't talk one word of business.

TMZ Sports spoke with Dana White about his visible hangout with Punk seen by millions on Pay Per View ... and the UFC Prez says they were just watching the fight as friends.

Dana adds, "He is a friend and a fan. We have literally never talked about wrestling or fighting or anything else work related since I've known him."

As we previously reported ... Punk quit the WWE in January after feeling like he was getting snubbed out of a main event match at "Wrestlemania XXX". Earlier this week Vince McMahon told investors the wrestler is currently "taking a sabbatical" from the company.