Begin by cooking the rice noodles according to package instructions. Once cooked, rinse under cold water to stop the cooking process and set aside.
In a large wok or frying pan, heat the coconut oil over medium heat. Add the sliced onion, garlic, ginger, and red chili. Sauté for about 3-5 minutes until the onions become translucent and fragrant.
Sprinkle the yellow curry powder into the wok, stirring for about 1 minute to toast the spices and release their flavors.
Pour the coconut milk into the pan, stirring well to combine with the sautéed aromatics and spices.
Add the soy sauce and fish sauce (if using) to the coconut milk mixture. Allow it to simmer for about 5-7 minutes to thicken slightly.
Stir in the sliced bell pepper and cook for an additional 3 minutes until they start to soften.
Add the cooked rice noodles to the wok, gently tossing them with the curry sauce until well coated and heated through. Add bean sprouts and toss for another minute just to warm them.
Remove from heat and stir in the chopped spring onions. Serve the noodles hot, garnished with fresh cilantro and lime wedges on the side.