I wanted to mention that the zero dollar fares are still available and not only between SIN and KUL but to many of the destinations flown by Air Asia. I just booked six flights to various parts of Malaysia, for just the cost of taxes and fees. KUL to KCH came out to USD 22. ^

Also, I noticed that when selecting express boarding for flights between SIN and KUL, it actually does not appear to charge the express boarding fee.