1. Preheat oven to 375 degrees F (190 degrees C). Line a roasting pan with aluminum foil.
2. Stuff the cavity of the snapper with 1/2 cup basil leaves and set aside. Heat the peanut oil in a large skillet over high heat until it begins to smoke. Place the snapper in the skillet, and quickly brown on both sides, about 1 minute total. Place the fish into the roasting pan, and sprinkle with fish sauce. Reserve the peanut oil in the skillet.
3. Bake fish in preheated oven until the flesh flakes easily with a fork, 25 to 30 minutes.
4. Meanwhile, heat the remaining peanut oil over medium heat. Stir in the garlic, ginger, chile peppers, and yellow pepper and cook until the peppers have softened, about 5 minutes. Stir in the sugar, rice vinegar, water, and tomatoes. Bring to a simmer over medium-high heat until thickened to desired consistency. Pour the sauce over the snapper, and garnish with the remaining basil leaves to serve.