Place scallops in a medium bowl and add tamarind. Pour in lemon juice, lime juice and pineapple juice, just enough to cover. Gently stir and press down lightly on the scallop mixture, making sure the seafood is submerged. Transfer to the refrigerator for 2 ½ to 3 hours or until the scallops turn opaque.
About 5 minutes before serving, in another bowl combine diced pineapple, white onion, red pepper, salt and black pepper; stir. Remove scallops from the fridge and using a slotted spoon, transfer scallops to the onion mixture. Pour in about 2 tablespoons of the liquid from the bowl. Add oil, stir, taste and adjust if needed. Then add parsley just before serving with tortilla chips.