Bring a large pot of water to just under a boil and add the noodles. Remove from heat and allow noodles to soak 5-8 minutes, or until soft but still chewy. Drain and rinse briefly with cold water to keep from sticking.
Using a large soup pot, bring chicken stock to a boil over high heat. Add the leftover turkey, lemongrass, ginger, carrot, bay leaf (plus chicken or turkey bones, if available). Boil on high for 1 minute, then turn heat down to medium and cover with a lid. Allow soup to simmer for 5-6 more minutes, adding Bok Choy when the turkey has heated through. Add chilli, garlic, lime juice plus fish sauce. Stir well.
Turn heat down to a simmer and add coconut milk.
Taste-test the soup, adding more fish sauce until desired flavour/saltiness is reached (how much you will need depends on how salty your stock is). If it tastes too salty, add another squeeze or two of lime juice. Add more chilli if not spicy enough, or more coconut milk if the soup is too spicy. If the soup is a little too sour for your taste, add 1-2 tsp sugar (to balance out the lime juice).
To serve, place a generous mound of noodles in each bowl, then top with the hot soup. Finish with a final sprinkling of pepper and fresh coriander. ENJOY!