Both the Malaysian and the Singapore internal intelligence services have a long and deep history of handling clandestine matters well because of their past experience in handling such issues. Both services have also largely been spared from the hubris that have impacted their respective public services such as politicisation.
Both also have have stuck to the traditional approach of recruitment where they pick candidates from a proven and established background from a pool rather than direct entry. And recruitment has no age limit. Someone can enter the service in their 30and 40s if their skills and aptitude is recognised and needed.
In terms of handling deviant Islam which is the topical issue for many countries, the approach by these 2 countries are similar - grassroots penetration and control, not only at core but all the way to the fringes. For an incident to occur, multiple measures have to fail and the probability is small.
In terms of non-Islam related terror - you are probably looking at something similar to the Laju incident where Singapore per se was not the issue but the presence of external actors who have a presence in Singapore and attract their natural enemies into Singapore such as Israel.
Singapore interestingly is not an ideal location or attraction for ideology based terror groups as we are basically are a desert barren of any ideology or philosophy. If attacked it will not be an effective rallying point for followers of any deviant ideology. Even if they bring down an entire skyscraper it will not register in the minds of their followers as any sort of an accomplishment.
That leaves Singapore to one oddity - any incident where the trigger is something more benign. An example is the rioting by drunk Indians at Little India. No planning, fuelled by alcohol and a Police Force caught out by incompetency and poor leadership.