Soak dried chilies first in hot water for 10 minutes until they become soft.  Put the chilies, shrimp paste, and garlic in a mortar and crush them with a pestle until smooth.  Heat the oil in a wok and stir-fry the paste from the mortar for 2 minutes.  Add the water spinach, and continue stir-frying fro 5-8 minutes until the spinach is tender.  Add the lime juice and adjust the seasoning.  Serve straight away as an accompaniment to a main dish.