To make the salsa, combine the pineapple, mango (if using), jalepeno, red chili, cilantro, lime juice and salt. Toss well, cover and store in the fridge until ready to serve.
To make the wings, preheat oven to 400°F and set a wire rack inside of a large rimmed baking sheet. Place the wings, oil and a pinch of salt in large bowl; toss to coat. Spread the wings out in a single layer over the prepared rack.
Bake wings until cooked through and skin is crispy, 45–50 minutes.
Meanwhile make the sauce. Combine the coconut milk, peanut butter, sweet thai chili sauce (start with 3/4 cup and then add more as desired), soy sauce, lime juice, ginger, brown sugar and lemon grass. Whisk until smooth and pourable. Taste and adjust spiciness to your liking.
Line another rimmed baking sheet with foil and top with a wire rack. Add half of wings to peanut sauce and toss to evenly coat. Place wings in a single layer on prepared rack. Repeat with the remaining wings and bake until glaze is glossy and lightly caramelized, 5–10 minutes. Garnish the wings with cilantro and peanuts. Serve alongside the remaining sauce and pineapple salsa.