Put the water, onion, celery, and corn in a large soup pot and bring to a boil over medium-high heat. Decrease the heat to medium and cook, stirring occasionally, until the vegetables are almost tender, about 15 minutes. Add the tomato paste and stir until well combined. Add the beans, greens, bell pepper, garlic, oregano, thyme, and salt. Cook until the vegetables are tender, about 5 minutes.