For the salad, wash the cucumbers and slice or cut them into fine slices. Peel and halve red onions and cut into fine strips. Mix vinegar, salt, pepper and 2 tablespoons of sugar. Fold in 1 oil and chilli oil. Mix in cucumbers and onions, cover and let it simmer for about 30 minutes.
In the meantime, peel and halve the remaining onions and cut into fine strips. Clean the chillies, cut lengthwise, remove seeds, wash and cut into fine rings. Wash and halve the tomatoes.
Rinse fish, dab dry and cut into cubes of approx. 3 cm. Mix flour and curry powder, turn fish pieces in it. Heat 4 tablespoons of oil in a large frying pan. Sauté the fish in it in portions for about 2 minutes while turning, remove and let it drip off on kitchen paper.
Heat 2 tablespoons of oil in a saucepan. Sauté onions and half of the chili for about 2 minutes. Stir in curry paste and deglaze with coconut milk. Simmer for 2-3 minutes. Add tomatoes and fish pieces and warm up. Season to taste with salt and pepper.
Wash the parsley, shake dry and pluck off the leaves. Season fish curry with lime juice if necessary. Serve with the cucumber salad, sprinkle with parsley and the rest chilli. Thin flat bread tastes good with it.