Make a paste by combining the chilies, shallots, fish sauce, chili powder, cumin, lime juice, garlic, ginger, lemongrass and coriander in a blender and puree until smooth. Place the snapper on a platter. Brush the paste all over the snapper and let sit, refrigerated, for 30 minutes.
Bring a large pot of water to a boil. Add the reserved seeds and ribs from the chilies and peels from the ginger, garlic and shallots to the water. Place a steamer basket on the pot. Place the bok choy in the base of the steamer basket and layer with the fish. Cover and steam until cooked through, about eight minutes.
Remove the bok choy and snapper from the steamer and sprinkle with the cilantro. Serve with lime quarters.
