This is not good news for budget travelers to Singapore, the airport authority is increasing taxes by $6 SGD, (~$38 HKD.) As you were probably aware, Tiger Airways and Jetstar Asia both ply the HKG – SIN route multiple times daily, and have very cheap fare sales usually, less than $800 HKD each way. Now with the increased taxes started April 1, 2013 I think they will have a harder time keeping the total fare below this amount.
If you’re very budget constrained, I’d try to book flights as early as possible so try to catch the lower taxes before the airline systems are amended. According to the article, the new taxes will be collected starting November 2012 for travel on or after April 1, 2013. As of today, Tiger and Jetstar are still showing the same taxes for flights prior to and after April 1, 2013.
Details can be found in this article