Place bacon in a large, deep skillet. Cook over medium-high heat until evenly brown. Drain, crumble and set aside.
Meanwhile, bring a large pot of salted water to a boil. Add potatoes and cook until tender but still firm, about 15 minutes. Drain, cool, and chop into bite-size chunks.
To make the dressing, mix together the mayonnaise, sugar, soy sauce, sesame oil, mustard powder, and salt.
Combine the potatoes, bacon, bok choy, red pepper, green onion and cilantro in a large bowl. Pour over dressing and mix well. Refrigerate for at least one hour to allow flavors to blend, and serve.
