Selena Gomez Body Banging, Bikini Clinging ... Pinky Swear

4/16/2015 7:27 AM PDT BY TMZ STAFF

0415-selena-gomez-akmgsiSelena Gomez didn't pull any strings in Puerto Vallarta ... dammit. 

Biebs' former squeeze was showing off the goods during her Mexican vacay ... sporting a double-stringed bikini bottom thingy (we know fashion).

There's not a ton of material to her ensemble, but what there is -- is definitely working overtime to cover the 22-year-old's assets. Things are getting thick down in Mexico.

It's high-season for tourism.