In a pot over medium heat, heat oil. Add onions, ginger, and garlic and cook until softened.
Add chicken and cook, stirring occasionally, for about 5 to 7 minutes or until chicken starts to change color and juices run clear.
Add fish sauce and cook, stirring occasionally, for about 1 to 2 minutes.
Add water and bring to a boil, skimming scum that floats on top. Lower heat, cover and simmer for about 30 to 35 minutes or until chicken is cooked through.
Add papaya and cook for about 3 to 5 minutes or until tender yet crisp.
Season with salt and pepper to taste.
Add spinach and push down into broth. Cook until just wilted. Serve hot.
