Heat 2 tablespoons olive oil in a large skillet over medium-high heat. Add 2 diced bell peppers, 1/2 to 1 sliced red serrano chile and 2 smashed garlic cloves. Season with salt and cook, stirring, until the peppers are lightly browned, 6 to 8 minutes. Add 6 chopped heads baby bok choy; cook until tender, 5 to 7 minutes. Stir in 1 tablespoon rice vinegar. Remove from the heat; stir in torn basil and season with salt.