In a large pot, blanch the pork ribs in boiling water for 3 minutes to remove impurities. Drain and set aside.
Heat a little oil in the pot and sauté the onion until soft.
Add the pork ribs, tomatoes, and carrot slices, cooking for 5 minutes.
Pour in water or broth, then add the soy sauce and sugar. Bring to a boil.
Lower the heat and simmer for 30-40 minutes, until the ribs become tender.
Add the corn and cook for an additional 10 minutes.
Season with salt and pepper to taste.
Serve the soup hot, garnished with fresh parsley or cilantro.