Demi Lovato Flaunts Sandy Butt Cheeks In The Bahamas

Demi Lovato's secret to summer smiles ... face in the sand, booty in the air ... literally!

Check out the gallery ... the singer shared a killer lineup of sexy snaps on her page -- soaking up the sun in the Bahamas and displaying her hot bod with her sandy backside taking center stage.

Rockin' with a variety of stringy bikinis, Demi turned 34 last week, and she's rounding out her birthday month with these top-tier shots from abroad.