Who can assist me in getting a permit. Thai airways has not been helpful. What about my Hotel?

I am traveling from U.S. to Thailand for a week and then returning from Thailand to the U.S. through Beijing and want to use the 72-hour VISA exemption so we can spend two days in China.. I have a separate ticket for this return trip. However, I understand that I need a permit to take advantage of the 72-hour exemption. . How can I get a permit now before my travels start on March 1? Thai Airways has not been helpful. Can the Concierge at the Grand Hyatt assist me in this matter?