Kevin Durant -- Blowin' Hookah Smoke

With 46 days 'til the NBA's opening day, Kevin Durant is in hardcore relax-mode -- with hookah pipes and Segway scooters.

The 24-year-old Oklahoma City Thunder superstar was rollin' around Barcelona yesterday on the two-wheeled machine (sportin' a helmet for safety) ... before chillin' out at a smoke shop.

Durant seems to be a big fan of hookah shops -- he's been spotted puffin' away all over the world in places like Chicago, Minnesota and even Hong Kong.

Kevin's penchant for puffin' might also explain why he was chillin' with Justin Bieber recently -- those guys might have more in common than we thought.