Combine the marinade ingredients in a mixing bowl and mix well. Add the fish and turn to coat in the marinade, then cover and marinate for 10 minutes. Drain off and reserve the marinade. Place a wok or frying pan over a low heat. Add the vegetable oil and palm sugar and cook until the sugar has caramelised, stirring slightly.
Add the garlic and pork belly and stir-fry for 15 seconds, then immediately add the marinated fish. Coat the fish with the caramel, then add the reserved marinade and cook for 1 minute.
Stir in the coconut juice and simmer for a further 6 minutes, skimming off any impurities that rise to the surface.
Serve sprinkled with the spring onion, pepper and chilli.