Peel papaya skin. Cut papaya lengthwise into 4-6 pieces, remove seeds and slice diagonally about 1 cm thick. Set aside. In a deep soup pot over medium heat, saute galic in oil until lightly browned. Add ginger and onion, stir for a minute. Add chicken pieces and fish sauce. Cook for 3 minutes. Add water. Season with a little salt and pepper. Let boil, then simmer covered over medium low heat for 25 to 30 minutes. Add raw papaya and continue cooking for 6 to 8 minutes or until tender. Correct seasonings to taste. Turn off heat. Add spinach, cover for 1-2 minutes. Serve immediately. Serves 4-5. Note: If green papaya is not available, substitute with potatoes.