Cook noodles in boiling water 5 minutes or until done. Drain and rinse with cold water; drain well. Set aside.
Heat oil in a large Dutch oven over medium-high heat. Add onion; sauté 4 minutes or until tender. Stir in 2 cups of water and the next 9 ingredients (water through bamboo shoots). Bring to a boil; reduce heat, and simmer 30 minutes.
Combine cornstarch and 2 tablespoons water in a small bowl. Stir cornstarch mixture into soup. Bring to a boil; cook 1 minute, stirring constantly. Stir in chicken; cook 3 minutes or until chicken is done. Place 1/3 cup noodles and 1 1/2 cups soup into each of 6 large soup bowls. Sprinkle 1 teaspoon cilantro over each serving.
Made half the recipe for lunch (I ate one portion, husband ate two). Totally eliminated the water! Who would put water in a soup? And that would be too much liquid, too. I just used the amounts of chicken broth and coconut milk indicated. Added a stalk of lemongrass finely chopped, along with minced ginger and kaffir lime leaves. Don't like canned straw mushrooms, so added some peas and minced red bell pepper. Also used 1/2 TB of green curry paste for just half the amount of other ingredients--so if you actually like strong Thai flavors, you'll want more than the measly tsp. indicated in the recipe. Very filling as a lunch dish--didn't really need anything else.