19-year-old May Ling is being dubbed "Thickest Teen on Planet" after getting a couple BBL surgeries ... but the buck -- or rather, the butt -- doesn't stop there ... she's going for an even bigger title. Check out the gallery ... May is already thicker than a bowl of oatmeal, but it's not enough in her eyes ... she's now looking to get the biggest BBL of all time and, to do so, she is on a 6,000-calorie diet and undergoing a buttload of surgeries to shape her body. The humble goal for 19-year-