Begin by preparing the aromatics at room temperature (Ihanda ang mga pampalasa): Clean and trim lemongrass stalks, then pound the white parts to release flavors (Linisin at putulin ang tanglad, at dikdikin ang puting bahagi para lumabas ang lasa). Julienne the ginger, slice onions thinly, and mince the garlic (Hiwaing pahaba ang luya, hiwaing manipis ang sibuyas, at dikdikin ang bawang).
Heat oil in a large heavy-bottomed pot over medium heat (350°F/175°C). Sauté onions, garlic, and ginger until aromatic, about 2-3 minutes (Igisa ang sibuyas, bawang, at luya). Add chicken pieces and cook until lightly browned, 5-7 minutes (Idagdag ang manok at lutuin hanggang bahagyang kumulay brown).
Add fish sauce and cook for 1 minute (Idagdag ang patis at lutuin ng isang minuto). Pour in coconut juice and bring to a boil over high heat (Ibuhos ang tubig ng buko at pakuluin). Once boiling, reduce heat to low and add lemongrass (Ibaba ang apoy at idagdag ang tanglad). Cover and simmer for 25 minutes.
Reduce heat to low (200°F/95°C). Add papaya chunks and cook for 3-5 minutes until tender but still firm (Idagdag ang papaya at lutuin hanggang lumambot pero hindi sobra). Add coconut meat strips (Idagdag ang strips ng buko). Season with salt and pepper to taste (Timplahan ng asin at paminta).
Add spinach leaves last and cover the pot (Idagdag ang spinach at takpan ang kaldero). Let the residual heat cook the spinach (Hayaang maluto ang spinach sa init ng sabaw).
Let the soup rest for 5 minutes before serving (Palamiguhin ang sabaw ng 5 minuto bago ihain). Serve hot with steamed rice (Ihain ng mainit kasama ang kanin).
When reheating, ensure the temperature reaches 165°F/74°C internal temperature (Kapag iinitin, siguraduhing umabot sa 165°F/74°C ang init sa loob ng manok).