Heat oil in a large pot or wok over medium heat. Add onions, garlic, and ginger; cook and stir until translucent, about 5 minutes. Stir in pickled cabbage. Add chicken; cook and stir until juices run clear, about 5 minutes. Add shrimp; cook and stir until starting to turn pink, about 2 minutes. Add fish balls and lotus root. Season with white pepper.
Pour chicken stock into the pot. Bring to a boil; reduce heat and simmer until fish balls float and lotus root is slightly tender, about 10 minutes. Stir in choy sum and bok choy stalks. Continue simmering until slightly softened, about 5 minutes.
Stir choy sum and bok choy leaves, chile peppers, salt into the pot. Simmer until leaves are wilted and flavors combine, about 5 minutes.
