Cook the noodles according to the package directions. Drain and set aside.
Meanwhile, in a large saucepan, over medium-high heat, combine the coconut milk, tomato paste, chili powder, salt, and chili paste (if desired).
Bring to a boil, then reduce heat and simmer for 2 to 3 minutes.
Stir the drained noodles into the sauce and toss. Divide among individual bowls. Top with the scallions, sprouts, basil, and coconut (if desired).