Peel the shrimp, reserving 6 shells; set shrimp aside. Heat the oil in a large Dutch oven over medium-high heat. Add the japones chiles and shrimp shells; sauté for 3 minutes or until the chiles are blackened. Add broth, and bring to a boil. Add galangal and next 5 ingredients (galangal through shallots). Cover, reduce heat to medium-low, and simmer 30 minutes.
Strain soup through a sieve into a bowl; discard solids. Return soup to pan. Increase heat to medium-high. Add shrimp and fish sauce; cook 2 minutes or until shrimp are done. Remove from heat; stir in lime juice. Sprinkle with cilantro leaves. Serve immediately.