Heat a large soup pot over medium-high heat and add 2tsp olive oil. Cut the sausage into slices and add to pan. Cook until browned, 8-9 minutes, using a wooden spoon. Remove from pan and set aside.
In the same pan, add diced onion, carrots and potatoes and 2 tablespoons oil . Add a pinch of salt and pepper to get the juices released from the veggies and cook until tender, about 7-8 minutes. Add garlic, chili flakes and bay leaf. Cook for 1 minute to release flavors then add the mung beans, cooked sausage, broth and diced tomato.
Bring pot to a boil then reduce heat to low. Simmer for 30 minutes or until beans are tender.