In Chinese culture, raises are mostly at the once per year performance review time.  Most Chinese are happy to be working, and having a clear idea of the salary structure.  They normally do not pay much attention to what other companies are paying their workers for a comparable performance. 
If you feel your performance deserves a raise, do ask your boss in a polite way for one.  But do your homework and have your arguments to support your petition ready in your mind, like extra work load, extra hours added, etc.
But above all, do not push your boss into a corner or use threats, you may get the raise on the short term, but in the long run you will have created an enemy.
If he is reluctant to give you one, try to negotiate for another face to face meeting on the same subject a few months in the future, when conditions may have somewhat improved nad your boss may be more willing to grant you one. 

Asking for a raise is almost a no-win-win situation here. Instead of asking for the all important raise I believe it's time to step into modern times a little. Asking for a raise is such a weak and archiac way to increase your income, I'm sure even the Chinese know that. Getting a raise because you think you deserve one is not a strong enough argument here or anywhere else, in my opinion.

Show your boss, (hopefully he is not a 2nd tier manager with no decision  making power) that you can actually help him increase his revenue as well. A true win-win situation. Tell him you would like a percentage of all new sales that you were involved in. If you teach and do nothing else to aid the owner in any way, I suggest asking for a raise is not a great idea. I have gotten two of my previous bosses to agree to a sliding scale based commission structure. Be creative and think of a workable plan before you go in asking for more money. Be ready for any possible comeback. Remember, you are already making as much as three or four of your local coworkers combined.

You could give them the old puppy dog look. They might think it's Gimme, Gimme, Gimme!! ME, ME, ME!! But then again if you don't try you will never succeed in what your trying to get! If words won't work you can always try the other message. Pictures tell a 1000 words give them a photo of some kind be creative and see if it works if the words you are asking won't!

.....and say don't ask. I said, be an adult with a plan and a purpose. Not a child hoping to get what you want because you believe you are entitled to it. The one child policy has created a nation of spoiled brats if you ask me.

Well, those individuals that I've known here have either known in advance what will happen with their pay as far as increases, and either accepted that, or moved on to another, better paying job.

As far as teaching, I think it's a little different. Firstly, if you're on a contract, you won't get a raise! If you're at the end of a contract, and you want to negotiate a new one with a higher pay, be prepared to find a new workplace if you're not happy with your current salary. Not that you won't get an increase, but that you must have an idea of what you are really worth. If you are happy working there, and they are happy with you, l point out why you should have one, and why they should give it to you. Point out the pay rates of others in similar situations (if theirs is better). Only compare pay in your own city, or similar cities. The last time I asked for a raise (possible contract renewal), they were only willing to give me another 10%... I got a job that pays more than double - but in a far better city, and far better employer! So, don't compare apples and oranges.

Just ask, that will never hurt. But also show enthusiasm and even suggest extra things you want to do for the business to warrant your potential raise. You are only worth more if you do more, otherwise you only get the standard little raises. May be tough to get though if you are in a contract in China.