Heat the vegetable oil in a large pot over medium heat. Add the pork tenderloin pieces and cook until lightly browned on all sides, about 5 minutes. Remove the pork and set it aside.
In the same pot, add the onion, garlic, and ginger. Cook for 3 minutes until the onion softens.
Stir in the Thai red curry paste and cook for 1 minute to release its aroma.
Pour in the light coconut milk, chicken broth, and fish sauce. Return the pork to the pot and bring the mixture to a simmer. Cook for 10 minutes.
Add the red bell peppers and simmer for 5 minutes more. Then stir in the baby bok choy and cook for 3 minutes until the greens wilt slightly.
Remove the pot from heat. Stir in the lime juice and zest. Serve the stew over cooked rice and top with fresh cilantro.