Lamar Odom -- Smiling & Friendly ... At Vegas Boxing Event

Lamar Odom is turning to some famous boxers for support in the wake of the death of his close friend Jamie Sangouthai ... hanging with Adrian Broner and Zab Judah at an event in Vegas.

Odom had briefly returned to L.A. after he learned Jamie died -- and as we reported, he was taking the death very hard and friends were concerned that he would relapse.

But Odom is now back in Vegas ... and today, he was supporting Broner as the boxer weighed in for his big fight against Shawn Porter tomorrow night.

We're told Lamar has been friends with Zab for years (they're both from NY) and made plans to hang out this week while supporting Broner.

Odom appeared to be in a good mood at the event, smiling and talking to people.