Heat the vegetable oil in a large pot over medium heat. Add the shallot and ginger and cook, stirring, for 1 minute to soften. Stir in the tamari, curry powder, coriander, cayenne, sugar, and salt and pepper to taste.
Stir in the broth and then add the squash. Bring to a boil and then reduce the heat to a simmer. Cover and cook for 20 minutes or until the squash is tender. Add the bok choy and simmer for another 10 minutes.
While the vegetables are cooking, soak the rice noodles in a bowl of hot water and set aside. When the noodles are soft, drain them and add them to the vegetables.
Stir in the coconut milk and heat until hot—but do not boil. Taste and adjust the seasonings if needed.
Serve in large bowls and garnish with cilantro and scallions. Serve with lime wedges and sriracha (if using).