When your smooth, hairless legs are worth a FORTUNE, ya flaunt what ya got ... at least according to international soccer superstar Neymar -- who busted out some ultra-micro tiny swim trunks this weekend in Vegas.
The Brazilian sensation -- easily one of the top 5 players in the world -- hit up the Encore Beach Club at the Wynn Las Vegas ... where he took in some sun before UFC 189.
During the pool party, Neymar kicked it with a ton of huge stars -- including Team USA champ Christen Press (above) ... and Houston Rockets superstars James Harden and Trevor Ariza.
FYI -- we're told Harden was WITHOUT Khloe Kardahsian this time around ... but it's not like he was out lookin' for chicks. We're told he kicked it in a cabana with a bunch of his guy friends.