In a pot, combine mung beans and water. Boil and simmer until the beans are tender. This would probably take about an hour. Set a side.
In a pan, combine pork fat and water. Boil and simmer over low heat for 40 to 60 minutes or until the fat or meat is tender. Increase heat to evaporate the remaining water. Stir fry the pork in its own oil until golden brown. Add oil if using lean meat.
Sauté ginger, garlic and onion.
Add tomatoes, bouillon cube and half cup of water. Boil and simmer for 15 minutes or until tomatoes are tender. Mash the tomatoes using the back of your wooden spoon.
Add the mung beans with the boiled water. Add more water if needed. Season with fish sauce and ground black pepper. Simmer for 10 minutes.
Add the okras and simmer for another 10 minutes. Garnish with onion spring.