1Add lemon grass, galangal and lime leaves to the 9 cups of water in a pot. Bring this to a boil.
3Once the water has reached a boil, turn the heat down to a simmer and add in the pork ribs and close the lid and let it simmer gently for about 20 minutes.
5Add in the fish sauce, salt, sugar, tomatoes and chilies, and boil for 2 or 3 minutes, or until the tomatoes have cooked and softened.
7Turn off the heat and then add in the cilantro, the green onions and the lime juice.
9Taste and adjust seasonings as necessary