Transfer the meat/kroeung mixture into a large soup pot, and cover it with water. Cover the pot and let it cook to a boil. Once it boils over, lower the heat to a simmer (medium-low). When the meat is tender, add water spinach stalk and celery. Adjust the taste to suit your palate – add sugar if you want a bit of sweetness ( I don't use sugar in mine), more prahok or fish sauce for a saltier taste, more tamarind juice for tartness. Once everything is cooked, add the water spinach leaves and basil leaves. Turn off the heat right away as you don't want to overcook the leaves. Most families don't add the water spinach leaves, but we do, since I like the taste of it, and it's wasteful to not use everything.