Pour oil into large wide-bottomed stockpot or Dutch oven and set over medium-high heat. Add garlic, onion, celery, and wild rice, and sauté 2 to 3 minutes. Lower heat to medium and add green bell pepper, red bell pepper, string beans and corn. Sauté and stir 1 minute. Next, stir in tomato sauce, white rice, and water, followed by fresh thyme leaves or dried thyme, salt, and black pepper. Semicover and cook over low-medium heat 20 to 25 minutes, then use large spoon to stir and push rice grains away from sides of pot. Cover and continue to cook over low heat another 10 to 15 minutes, until all liquid has been absorbed and rice grains are fluffy.