Heat the oil in a large nonstick wok and add the curry paste. Stir-fry for 1–2 minutes and then add the coconut milk. Bring to the boil, reduce the heat and simmer gently, uncovered, for 6–8 minutes.
Add the fishballs, palm sugar, lime leaves, lemon grass, fish sauce and bean sprouts. Bring to the boil, reduce the heat again and simmer, uncovered, for a further 6–8 minutes.
To serve, ladle the curry into bowls, garnish with sliced red chilli and fresh coriander and serve with steamed jasmine rice.