Ingredients
2 teaspoons sesame oil 
1 tablespoon minced fresh ginger 
2 teaspoons red curry paste (such as Thai Kitchen) 
1 (32-ounce) container fat-free, less-sodium chicken broth, divided 
2 1/2 cups water 
1 (13.5-ounce) can light coconut milk 
1/2 cup fresh lime juice (about 6 limes) 
3/4 pound skinless, boneless chicken breast halves, cut into 1/2-inch pieces 
1 (8-ounce) package presliced mushrooms 
3/4 cup chopped green onions (about 5 onions) 
1/4 teaspoon salt 
1/3 cup chopped fresh cilantro 
Lime wedges
Directions
Step 1
Heat sesame oil in a Dutch oven over medium heat. Add ginger; sauté 30 seconds. Add curry paste; sauté 30 seconds. Add 1 cup broth, whisking until curry paste dissolves; add remaining broth and water. Bring broth mixture to a boil; cover, reduce heat, and simmer 10 minutes.
Step 2
Add coconut milk and next 5 ingredients. Bring to a boil; reduce heat, and simmer, uncovered, 3 minutes or until chicken is done. Stir in cilantro. Ladle soup into individual bowls. Serve with lime wedges.
Source: 
http://www.myrecipes.com/recipe/thai-chicken-soup