Place chiles on a foil-lined baking sheet; broil 10 minutes or until blackened, turning occasionally. Place in a zip-top plastic bag, and seal. Let stand for 15 minutes. Peel chiles; cut in half lengthwise. Discard seeds and membranes; chop chiles, and set aside.
Bring water, thinly sliced garlic, and bay leaves to a boil in a saucepan; add chicken. Reduce heat; simmer 20 minutes or until chicken is done. Remove chicken; cool. Strain broth through colander into a bowl; discard solids. Reserve 1 cup broth. Shred chicken with 2 forks.
Preheat oven to 425°.
Combine flour and salt in a bowl; gradually add milk to flour mixture, stirring constantly with a whisk. Melt butter in a medium saucepan over medium heat; add oregano, cumin, and minced garlic, and sauté1 minute. Add flour mixture and reserved 1 cup broth, and cook until thick (about 4 minutes), stirring constantly with a whisk. Remove 1 cup sauce; set aside. Add 1/2 cup chiles and corn to remaining sauce in pan; cook 2 minutes over medium-low heat. Remove from heat; stir in cheese. Combine chicken, reserved 1 cup sauce, and remaining 1/2 cup chiles in a bowl.
Spoon about 1/4 cup chicken mixture down center of each crepe; roll up. Place crepes, seam sides down, in a 13 x 9-inch baking dish coated with cooking spray, and spoon cheese sauce over crepes. Bake at 425° for 15 minutes or until bubbly. Sprinkle with tomato.
Note: Two (4.5-ounce) cans of green chiles, drained and chopped may be substituted for poblano chiles.