Heat oil in a large soup pot, add the ham hock and sear on all sides for 4 minutes. Add the onion, celery, green pepper, and garlic, cook for 4 minutes. Add the black-eyed peas, stock, bay leaves, thyme, and seasonings. Bring to a boil, reduce the heat and simmer for 40 minutes, or until the peas are creamy and tender, stir occasionally. If the liquid evaporates, add more water or stock. Adjust seasonings, and garnish with green onions. Serve over rice.