Heat the vegetable oil in a large pot over medium heat. Add the red curry paste and cook for a minute until fragrant.
Add the chicken (or beef) to the pot and cook until browned on all sides.
Pour in the coconut milk, chicken broth, fish sauce, soy sauce, brown sugar, turmeric powder, and curry powder. Stir well to combine.
Bring the mixture to a boil, then reduce the heat and let it simmer for about 20 minutes to allow the flavors to meld together.
While the soup is simmering, cook the egg noodles according to the package instructions. Once cooked, drain and set aside.
Divide the cooked noodles among 4 serving bowls.
Ladle the Khao Soi soup over the noodles, making sure to distribute the chicken (or beef) evenly.
Top each bowl with bean sprouts, a squeeze of lime juice, and a sprinkle of fresh cilantro.
If desired, garnish with crispy fried noodles for added texture and crunch.
Serve hot and enjoy!