In a large saucepan, heat oil over medium. Add onion; cook until softened, 5 to 6 minutes. Add garlic and cumin; cook, stirring often, until fragrant, about 2 minutes more.
To the pan, add chiles, beans, tomatoes and their juice, 2 cups water, and 3/4 teaspoon salt. Bring mixture to a boil; reduce heat to medium-low, and simmer, partially covered, until slightly thickened, about 20 minutes.
In a blender or food processor, puree 2 cups of the stew. Return the puree to the pan, and add corn; simmer until heated through, about 5 minutes. Serve hot.