In a large pot, heat the coconut oil over medium heat. Once shimmering, add the finely chopped onion and sauté for about 5 minutes, until it becomes translucent and soft.
Stir in the minced garlic and grated ginger, cooking for an additional minute or until fragrant, stirring frequently to prevent burning.
Add the red curry paste to the pot, stirring constantly for about 2 minutes to release its rich flavors and aromas.
Gradually pour in the coconut milk and vegetable broth, followed by soy sauce, lime juice, and brown sugar. Stir thoroughly until all ingredients are well combined.
Bring the mixture to a gentle simmer, allowing the flavors to meld together for about 5 minutes.
Add the rice noodles to the pot, and cook according to the package instructions, which typically takes around 4-6 minutes. Stir occasionally to prevent sticking.
In the last 2 minutes of noodle cooking, gently fold in the trimmed snap peas, thinly sliced red bell pepper, and baby spinach. Stir to combine and cook until the vegetables are just tender yet still vibrant in color.
Before serving, taste the soup and adjust the seasoning if needed. You can add more lime juice for acidity or soy sauce for saltiness, according to your preference.
Ladle the hot soup into bowls, garnishing generously with fresh cilantro leaves and serving with lime wedges on the side.
Notes
For an appealing presentation, serve in wide, shallow bowls and garnish with cilantro and lime wedges.