This is also known as rice sticks and is available in Chinese groceries. A very delicate spice sold in powder form. Also known as kha in Thai cooking. Available in Asian groceries. A hard nut with lots of oil used to flavor curries. Also known as kemiri (Indonesian) or buah keras (Malay). Available in Asian groceries. Shell and devein prawns, reserving shells and heads. Drain these thoroughly. Remove any bones and skin from fish fillets and using a chopper, chop very finely. Mix in the salt and pepper and shape into small balls, or into a sausage-shaped roll and divide into finger-width slices. Pick over crab meat and discard any bony tissue, or chop the whole crabs into pieces after removing top shell and fibrous tissue. Heat 2 tablespoons oil in a saucepan and when very hot throw in the prawn heads and shells and fry until they turn bright red. Add 8 cups water and 2 teaspoons salt, cover and simmer 20-30 minutes, then strain. Discard shells and heads. Return the stock to the fire, drop in the fish balls or slices and the prawns, cut into pieces if large. Return to the boil, then lower heat and simmer for 3-4 minutes. Set aside and keep warm. Scald the rice vermicelli by pouring boiling water over it, then allow it to drain in a colander. Or soak it in warm water for 5-10 minutes, drain well. Scald the bean sprouts by pouring boiling water over. Rinse in cold water, washing off any loose skins. Pinch off straggly brown "tails." Slice spring onions finely, roughly chop mint leaves. Set aside each ingredient separately] until serving time. TO MAKE THE SOUP: Heat remaining 3 tablespoons oil and fry the onions, garlic, and lemon rind until onions are golden. Stir in the laos powder, candlenuts, chillies, blacan, turmeric and coriander. Add the prawn stock and when the soup comes to the boil add the coconut milk, sugar, and salt. Reduce heat and simmer, uncovered, for 10-15 minutes, stirring to prevent coconut milk curdling. In each bowl, arrange a ladle of the vermicelli, enough to two-thirds fill the bowl. Add a handful of bean sprouts, a tablespoon each of cucumber, and sliced spring onions. Add also a large pinch of mint. Pour the boiling soup over and serve immediately. A hot sambal can be served along with this for individuals to add to their portion if desired. Serves 8-10.