Sort peas and rinse with cold water. Place peas in a Dutch oven; add water to cover by 2 in. Bring to a boil; boil for 2 minutes. Remove from the heat; cover and let stand for 1 to 4 hours or until peas are softened. Drain and rinse peas, discarding liquid., Return peas to Dutch oven. Add 2-1/2 qts. water, ham bone, onion, salt, pepper, thyme and bay leaf. Bring to a boil. Reduce heat; cover and simmer for 1-1/2 hours, stirring occasionally., Remove the ham bone; when cool enough to handle, remove meat from bone. Discard bone; dice meat and return to soup. Add carrot and celery. Simmer, uncovered, for 45-60 minutes or until soup reaches desired thickness and vegetables are tender. Discard bay leaf.