In a large pot, heat the vegetable oil over medium heat. Add the diced onion and sauté until translucent, about 3-4 minutes.
Stir in the minced garlic and grated ginger, cooking for an additional minute until fragrant.
Add the red curry paste and stir well to combine with the onion mixture. Cook for 1-2 minutes.
Pour in the chicken or vegetable broth and bring to a simmer.
Stir in the coconut milk, fish sauce, and lime juice. Allow the soup to simmer for 5 minutes.
Add the shrimp, mushrooms, red bell pepper, and snap peas to the pot. Cook for another 5-7 minutes, or until the shrimp are pink and cooked through.
Taste and adjust seasoning if necessary. Serve hot, garnished with fresh cilantro and lime wedges on the side.