In a large stockpot, place chicken and enough water to cover. Add ginger and salt. Cover and cook over medium heat until chicken is tender, about 45 minutes to 1 hour. Allow chicken to cool in the broth, then remove from pot. Bone the meat and shred it, discarding the skin. Strain and reserve stock.
Soak the bean thread noodles in warm water for 15 minutes. Drain.
In a skillet, heat oil and saute onion, garlic and ginger until lightly browned. Add noodles and enough reserved chicken stock to cover. Add chicken and soy sauce and simmer until noodles are tender, about 5 minutes. Before serving, top with green onions.