A weapon isn't always necessary. If you're not gonna stick to the tourist areas that are going to be safer for the most part you just have to take some precautions. You just don't walk around with stuff on you that can be stealable, like backpacks, handbags etc. Put stuff in your front pockets. Stay in places with a decent amount of people so that you can't be taken and have a weapon held up to you.
Yeah, Hong Kong is probably the only place where I would put my wallet in my back pocket. The crime rate is so low. It makes it so easy to steal stuff. The 711's in the metro stations have no doors and the shelves are literally within a couple feet of the outside so you can just reach your arm in while walking by and grab something and hide it under your jacket if you're in a crowded place. And you can cheat the metro by jumping over that thing that turns and there aren't people around to catch you. I've done it a few times when I was low on money.