I agree 100% with Thai-Kiwi, Sam Drucker and Jie Jie.

The local Bangkok office is the best solution.

My experience is that even when fully booked and not available I have almost always got what I wanted.

Maybe it is a problem with all the extra offers of 50% off for Gold members and the recent 2 people fly for 50% of miles.

I have been looking at a reward ticket from LHR-BKK in October and there is little availability so it looks like a trip to Silom office when I get back from the Sunshine coast

Also remember that availabilty can open up and that the Fat Controller may release seats held for TIPs as suggested on this thread.