Wash the fish, dab dry and cut into cubes. Peel the pineapple, cut out the hard stalk. Cut the flesh into bite-sized pieces. Peel ginger and garlic. Grate ginger and chop garlic.
Prepare the pasta in boiling water according to the instructions on the packet. Heat the oil in a frying pan. Fry the fish cubes for about 2 minutes while turning. Add ginger and garlic and fry briefly. Add coconut milk, broth, chili flakes, pineapple, fish sauce, sugar and 1 pinch of pepper and simmer for about 4 minutes.
Wash the coriander, shake dry and, except for something to garnish, pluck leaves from the stems, chop them and add to the fish. Season with fish sauce and pepper. Drain the pasta, let it drain and arrange in bowls.
Pour pineapple fish sauce over it, garnish with coriander.