Heat the oil and red pepper flakes in a large stock pot or dutch oven over medium high. Sauté the chopped onions for a couple minutes until the onions begin to take on some color.
Add the green onions, carrots, peppers, tomatoes and sweet potatoes. Stir briefly to cover them with the oil and mix in the sautéed onions.
Push the veggies to the side to make space in the center. Spoon in the tomato paste, lemon grass and curry powder. Stir well to mix it together, then bring in the vegetables so everything is covered with tomato paste.
Add the bay leaves and pour over the broth and stir.
Cover with a lid, then lower the heat and simmer until the vegetables are just tender, stirring on occasion.
Stir in the tofu and coconut milk. Taste and adjust the seasoning as needed. The tofu should be heated through before serving.
To serve, arrange the garnishes on a small platter, spoon the soup into bowls and allow everyone to garnish as desired.