For the marinade:
1 cup coconut milk
5 chiles, finely chopped
1/2 onion, finely chopped
4 tablespoons light soy sauce
4 tablespoons oyster sauce
1 teaspoon finely grated fresh ginger
1 teaspoon finely chopped fresh coriander
1 teaspoon crushed garlic
4 red snapper fillets, skin on
1. To make the marinade: In a medium bowl, combine all marinade ingredients. Set aside.
2. With a sharp knife, score the fillets lengthwise in parallel lines about 3/4 apart. Place the fillets in a resealable plastic bag and pour the marinade over them. Press out the air and seal the bag tightly, then turn the bag several times to distribute the marinade. Set in a large bowl and refrigerate for at least 1 hour or preferably overnight, turning the bag occasionally.
3. Prepare the salsa just before grilling the snapper fillets: In a large bowl, mix the mango, cucumber, red pepper, shallots, cilantro, lime juice, and jalapeno. Season to taste with salt and pepper. Set aside.
4. Remove the snapper from the marinade and pat dry. Lightly brush the fillets with the oil and place them skin-side down on the cooking grate. Grill over Direct Medium heat for 8 minutes or until fish flakes easily with a fork, turning one halfway through grilling time.
5. Serve warm with the mango salsa.