I just changed my NRT-ORD ticket on AA to HKG-YYZ-ORD itinerary because after reading about AA's first class-I decided it would be worth the 150 change fee to have that fabulous CX suite and some pretty incredible food. Beats getting stuck with an entree you didn't want and having to eat at certain times.
I am sure you will not regret your decision. I am also going to Bangkok as well. Hope you have a safe trip!