Prepare Noodles: Cook the rice vermicelli noodles according to the package instructions. Drain and set aside.
Sauté Aromatics: In a large pot, heat the vegetable oil over medium heat. Add the chopped onion, garlic, and ginger. Sauté until the onion is translucent and aromatic, about 5 minutes.
Add Curry Paste and Spices: Stir in the red curry paste and turmeric powder. Cook for another minute, stirring constantly.
Add Liquids: Pour in the coconut milk and vegetable broth. Stir well to combine everything.
Season Soup: Add soy sauce, sugar, and lime juice. Bring the soup to a simmer and let it cook for about 20 minutes. Taste and adjust salt as needed.
Add Vegetables: Add the shredded cabbage and carrots to the soup. Cook for another 10 minutes, or until the vegetables are tender.
Assemble Bowls: Place a portion of the cooked noodles into each serving bowl.
Serve: Ladle the hot soup over the noodles. Garnish with cilantro, green onions, and any additional toppings of your choice.
Enjoy: Serve your vegetarian Khao Poon hot, allowing everyone to add more lime juice or chili to their taste.