SIN took a huge turn for the worse with regard to connecting times with the opening of T3 in January. They used to have security screening at each gate but now have combined security screening for multiple gates. With this new method come some absolutely huge queues at times. It has taken me nearly 45 minutes just to get to the front of the queue. For SIN being known for being efficient, they totally screwed up and it is one of the most inefficient airports around with respect to security. They had a sign to separate C, F, PPS, *A Gold passengers but nobody was enforcing it and both queues were equal in length. Other time's I've been there there's been almost no queues. It just depends on if you happen to get there when several gates in the same cluster are being used or not. If you're connecting to T2 then it should be no problem as it's as efficient as it's always been.