Heat vegetable oil in a large stockpot over medium heat.
cook and stir onion and garlic in the hot oil until onion is softened and translucent, about 10 minutes.
Add water, chicken base, potatoes, carrots, bok choy, and celery; bring to a boil. Reduce heat and simmer until vegetables are slightly tender, about 10 minutes. Add chicken; continue simmering until chicken is no longer pink in the center, about 10 minutes.