Mix ginger, lime leaves, chillies, lemongrass, coconut milk, lime juice, and fish sauce in a bowl.
Coat the fish fillets in the marinade and rest for at least two hours.
Preheat the oven to 180°C.
Place each fish fillet onto a sheet of baking parchment.
Strain the marinade and spoon the solids over the fish fillets, reserving the liquid.
Fold and seal the parchment edges to create parcels.
Place parcels on a tray and bake for 15-20 minutes.
Boil the reserved liquid in a pan for 3-4 minutes until slightly thickened.
Unwrap the fish and serve on plates with jasmine rice and the sauce.