CUT kernels from the cobs; reserve kernels and cobs. Place evaporated milk and corncobs in large saucepan; bring to a boil over medium-high heat. Reduce heat to low; cover. Cook for 8 minutes.
MEANWHILE, heat oil in large skillet over medium-high heat. Add onion; cook, stirring frequently, for 3 to 4 minutes or until translucent. Stir in carrot, celery, garlic and reserved corn kernels. Season with salt and ground black pepper. Cook, stirring frequently, for 5 minutes or until vegetables are tender.
ADD vegetable mixture, water and thyme in saucepan; cover. Cook over medium heat, stirring occasionally, for 20 minutes. Discard corncobs and thyme. Cool mixture for about 10 minutes.
POUR soup into blender until it is half full; cover. Blend until smooth. Pour through a medium sieve into clean saucepan (discard contents of sieve). Repeat process with remaining soup. Reheat soup until heated through. Serve topped with swirl of sour cream and chives.
Cook's Tip: Soup is also great served chilled.