If rimming glasses in coconut, place shredded coconut on a plate and lightly brush the rims of the cocktail glasses with simple syrup.
Place glasses on plate upside-down and roll gently until rims are coated in coconut.
In a blender, put ice, chopped pineapple, light coconut milk, tequila, and triple sec. Blend until smooth.
Divide drink into two glasses. Garnish with slice of pineapple and sprinkle with additional shredded coconut if desired.