Pour oil into heavy medium skillet to depth of 3/4 inch and heat oil to 350. Fry tortilla strips in batches until crisp and golden, about 1 minute. Drain tortillas on paper towels.
Transfer 1 tablespoon tortilla-frying oil to heavy large pot. Add onion and saute over medium heat until tender, about 5 minutes. Add garlic, chili powder, cumin, oregano and bay leaf. Saute 1 minute. Add chicken stock, tomato sauce, salt, sugar and pepper and bring to boil. Add chicken. Cover pot and simmer until chicken is just cooked through, about 15 minutes.
Using tongs, transfer chicken to plate and cool slightly. Cut away skin and bones from chicken; shred finely. Add 1 1/4 cups of corn to soup. Simmer until corn is tender, about 5 minutes. Add chicken to soup and simmer 1 minute.
Ladle soup into bowls. Garnish with tortilla strips, sour cream, radishes, cilantro, red onion and remaining 1/4 cup corn kernels.