Soak the dried chillies in hot water until softened for easier blending.
In a blender, combine softened chillies, onions, garlic, shrimp paste, and ½ cup of water. Blend until smooth.
In a basin, marinate the stingray with 2 tbsp of tamarind paste to remove any fishy odour. Set aside for 10 minutes.
Prepare tamarind water by mixing 3 tbsp tamarind paste with 2 cups of water.
Heat 5 tbsp oil in a pot over medium heat. Pour in the blended spice paste and stir constantly to prevent burning. Fry until the paste becomes aromatic, then add the bruised lemongrass stalk. Lower the heat if necessary.
Once the oil rises to the surface, pour in 2 cups of water and the prepared tamarind water.
Bring the mixture to a boil and allow it to reduce slightly.
Add the stingray and cover the pot.
Add laksa leaves and pickled mustard greens to your liking. Season with salt and pepper to taste.
Simmer until the stingray is fully cooked and the soup is rich in flavour.