Toronto Raptors star Scottie Barnes' Cancun vacation looks like a scene outta "High School Musical" ... 'cause the hooper showed off his awesome singing abilities during a karaoke session!! The 2021 No. 4 overall pick's offseason started early after the Dinos failed to make the postseason ... but…

Shaqtin' a Fool, anyone?? NBA rookie Scottie Barnes certainly earned his nomination ... 'cause the Toronto Raptors guard tripped and fell to the ground before facing off against the Grizzlies -- and it was hilarious!! In the video, you can see Barnes and his teammates were running out onto the…