Before you do anything else, you need to discuss your whole case with a divorce attorney.  Do not let your son go anywhere until you do.  Since your wife has ties to China and has found employment there you should seek legal counsel ASAP.

As for her or someone else taking him out of the country without your permission, that would be harder to do.  I assume that you are on the birth certificate and therefore the legal father; typically, before a child is allowed to travel to a foreign country, a permission authorization must be signed by the non-traveling parent(s) and then notarized.   

By the way, you shouldn't tip off your wife about retaining a lawyer any sooner than you have to.  You want to get your case in order as much as you can beforehand.

Again, see an attorney as soon as you can. 

You definitely need to get a lawyer, and proceed to get a custody order, otherwise once your child is in China you may not be able to get him back.

BARRY BESSER, www.besserlaw.com