In a large pot, heat oil over medium-high heat. Add onion, carrots, celery, salt and pepper. Cook until onions are translucent and vegetables begin to soften, about 10 minutes.
Add rinsed peas, water, bay leaf, and thyme. Stir to combine and bring to a boil. Reduce heat to medium-low, and simmer, partially covered for 50 to 60 minutes.