I have stayed twice at the GH SIN, on two different corp rates, never asked - I have also stayed at GH HKG, GH BKK, GH CGK, GH TPE and PH and GH NRT, different rates, never asked.

Fo the OP who asked the question, you should not worry about being asked. Many people in this forum have some issue with people using these codes, so that try to scare poeple. As mentioned, the worst that could happen is that the hotel, will charge you the full rate, that is very unlikly to happen. What will most likly happen is they won't program your room key correctly the first time.

Just so you know, they may ask for your busienss card to ensure they have your address and email informaiton correct for purposes of the registration card (for some reason reservations made at hyatt.com, don't always populate over to a printed registration card or for repeat guest they want to make sure info is most updated). You can always just tell them you don't have a card with you (many lower level employees who travel for business do not have busienss cards), and just fill out your address information. Simple fix to a not very complicated problem.

Safe travels OP!