Whisk soy sauce, vinegar, and cornstarch together in a small bowl.

Heat 1 tablespoon oil in a wok over medium-high heat. Cook and stir tenderloin strips in hot oil until just browned, 2 to 4 minutes. Transfer pork to a plate and return wok to heat.

Heat remaining oil in the same skillet over medium-high heat. Cook and stir red chile pepper and garlic in hot oil until sizzling, 15 to 30 seconds. Add onion and green pepper to skillet; cook and stir until onion starts to soften, 2 to 3 minutes. Stir chopped bok choy stalks into onion mixture; cook and stir until stems begin to soften, about 3 minutes.

Stir broccoli into bok choy mixture; cook and stir until slightly softened, about 2 minutes. Add pork, chopped bok choy leaves, and soy sauce mixture; cook and stir until well-combined. Season pork mixture with ginger; cook and stir until bok choy starts to wilt and broccoli is tender, 5 to 7 minutes.