Begin preparation by cleaning chicken thoroughly and cutting into serving pieces (Linisin ang manok at hatiin sa serving size). Pat dry with paper towels at room temperature.
Prepare the aromatics: Bruise lemongrass stalks to release oils (Dikdikin ang tanglad para lumabas ang lasa), chop onions, mince garlic, and julienne ginger (Tadtarin ang sibuyas, dikdikin ang bawang, at hiwaing pahaba ang luya). Prepare chilies, removing seeds if less heat is desired.
Heat oil in pot over medium heat (180°C/350°F). Sauté onions until translucent, about 2 minutes (Igisa ang sibuyas). Add garlic and ginger, sauté until fragrant, about 1 minute. Add chicken pieces and brown on all sides, 5-7 minutes (Igisa ang manok hanggang maging brown).
Add coconut milk and bring to a gentle simmer, not boiling (Ilagay ang gata at painitin ng dahan-dahan). Add lemongrass and chilies. Reduce heat to low (160°C/320°F) and cover. Simmer for 20-25 minutes.
Add papaya and cook until tender (Ilagay ang papaya hanggang lumambot). Season with fish sauce and salt to taste (Timplahan ng patis at asin).
Add spinach in the last minute of cooking. Maintain temperature at 160°C/320°F.
When reheating, ensure internal temperature reaches 165°F/74°C (Kapag iinitin, siguraduhing umabot sa 165°F/74°C ang init)