Heat vegetable oil in a large skillet over medium-high heat. Add garlic and ginger and cook until fragrant, about 30 seconds to a minute.
Add bok choy, soy sauce, and 2 tablespoons water. Cover and cook 1 minute, then remove lid and cook, stirring occasionally, until cores are tender and all liquid has evaporated. Transfer to a serving dish, drizzle with sesame oil and sprinkle with sesame seeds, if using.