Combine ginger, garlic with stock in a heavy saucepan.
Wash and drain chicken thighs and add to stock mixture with salt. Simmer, uncovered, until chicken is cooked through, 25 to 30 minutes. Skim through out the cooking process.
Transfer chicken with a slotted spoon to a cutting board and cool.
Shred meat into 1/4-inch-thick pieces, discard the skin and bones.
Stir noodles into broth and simmer, uncovered, until noodles are translucent, about 6 minutes.
Stir green onions into broth along with chicken. Adjust seasoning with shoyu and chilipepper water.
This dish is great for using the left over carcass of a roasted chicken. Follow instructions replacing the thigh for the carcass. You can also use thigh meat and a carcass to get more flavor into the broth.