Simmer chicken bones and rib bones (optional) for about 30 minutes in water to make the stock. (if rib bones is used save the meat for garnishing.)
Shell prawns. Wash prawn shells and heads and flower crabs and boil in a little water. When boiled, strain prawn and crab stock into the meat stock. Boil the shelled prawns and save the water to add into the main stock.
Fry the ground chillies, shallots and garlic in 3-4 tbsp cooking oil till aromatic. Then pour into the main stock and simmer over a slow fire till ready for serving.
To serve, scald required amounts of beansprouts, kangkong and mee or beehoon and place them it into a bowl. Scoop generous ladles of soup over the mee and beehoon and vegetables.
Garnish with meat, prawns and hard-boiled egg slices. Sprinkle some fried shallot crisps and serve with chilli sauce and a dash of chilli oil.
To make chilli oil: Stir-fry 2 tbsp chilli boh with 1/2 cup cooking oil till fragrant and aromatic and oil rises to the top. Add a pinch of salt and set aside.