1, Prepare a hot fire for direct-heat grilling in a charcoal grill (you should be able to hold you hand 1 to 2 inches above the grate for only 2 to 3 seconds). When the coals are ready, place a cast-iron griddle or large cast-iron frying pan on the grill grate and let it preheat until very hot.
2, While the fire is reaching temperature, rinse the fish in cold water and pat dry with paper towels. Season the fish inside and out with salt and pepper, then stuff the cavity with the ginger, basil, cilantro, and lemon and lime slices. Drizzle the oil on both sides of the fish and set aside.
3, To make the sauce, in a small bowl, stir together the lime juice, fish sauce, sugar, ginger, garlic, and Thai chile until the sugar has dissolved. Set aside.
4, When the griddle or pan is very hot, add the fish and cook it without moving it for about 6 minutes until the skin is a deep golden brown and is no longer sticking to the griddle. To check, gently try to lift the fish; if it does not release easily, continue to cook until it does.
5, With a large, wide spatula centered at the middle of the fish, flip the fish and cook on the second side until golden brown. After 1 minute, begin checking to see if the fish is done. Insert the tip of a knife into the fish and wiggle it gently; the flesh should be barely clinging to the bone. If you feel resistance, continue cooking, repeating the test until the flesh offers no resistance.
6, Transfer the fish to a platter and serve immediately. Accompany with the dipping sauce.