Prepare 8 wooden skewers by soaking them in cold water until needed. Prepare the chillies by removing the stalks and seeds. Remove as much membrane as possible, then roughly chop the chillies.
Add the chilli, garlic and ginger to a mortar along with ½ tsp salt and grind with a pestle until the ingredients are combined and pulpy. You can also use a mini processor, though you might need to finish it off in the mortar. Stir in the lime juice, fish sauce and sugar, adding more salt and sugar according to your taste. Transfer to a large bowl.
Add the pork and pineapple to the bowl of sambal and toss together until coated. Cover and leave to marinate for at least an hour. Alternate threading the pineapple and pork on to 8 skewers, saving the marinade. Place a large griddle pan over a medium/high heat. While it heats, add the marinade to a small saucepan and bring to the boil for 2-3 minutes until slightly thickened.
Add the skewers to the griddle for 10-12 minutes, turning frequently until caramelised and cooked through, occasionally basting with the leftover marinade. When ready to eat, arrange the kebabs on a platter, scatter with the coriander and serve with extra lime wedges