Heat a medium soup pot over medium-high heat. Add vegetable oil, 3 turns of the pan, crushed red pepper flakes, garlic, ginger, mushrooms, and bok choy, then season with salt and pepper. Add chicken broth and seafood stock or clam juice. Put a lid on the pot and bring soup to a boil.
Add shrimp and noodles and cook 3 minutes. Add in scallions and cook 2 minutes, then turn off soup and let it sit 2 to 3 minutes more. Adjust salt and serve.