In a large pot, add 2-3 tbsp oil, 5 cloves garlic, 1 cup scallion whites, 1 inch sliced ginger, 2 pieces smashed lemongrass and saute for 2-4 minutes until very fragrant and slightly browned.
Remove large lemongrass pieces, then add 1 pound spinach leaves. Saute briefly just to wilt the leaves slightly. Add 4 cups chicken broth. Stir. Add 1 bunch of cilantro leaves. Combine, then use an immersion blender to puree the contents of the pot. Once fully smooth, add lime juice and 1 tbsp fish sauce along with 1 tsp kosher salt.
Whisk in 1 can coconut milk. (Reserve a small amount for garnish, if you want) Taste and adjust seasonings as needed.
Add cooked white rice to a bowl and pour the soup over it. Garnish with chili oil, lime juice, cilantro, and remaining coconut milk as desired.