Justin Bieber's Pal -- I'm No Coke Smuggler ... I'm Just a Mogul!

Justin Bieber's pal --and prolific music producer --Jason "Pooh Bear" Boyd is blasting reports insinuating he's involved in international cocaine smuggling and corrupting the Biebs.

Boyd tells TMZ ... he's NEVER been a drug seller in any "way, shape, form or fashion."

As for what Boyd was holding in the Instagram pic Justin posted Tuesday ... he's scoffing at reports that it's white powder. Boyd says it's actually a piece of FRUIT -- a slice of LIME.

And one more thing ... Photos surfaced this week showing Boyd with government officials in Suriname. One of the officials had a drug conviction. Boyd says it was all just a photo op connected to a Rick Ross rap concert in the country ... a concert he produced.