Dunno if your SingTel broadband service is DSL or cable. If the
latter, it might be interesting to find out if other ST broadband
subscribers on the same network in your immediate vicinity are
experiencing the same problem. If so, then it might simply be a
network capacity problem.
Does the problem occur during non-peak hours of usage, like at 5
a.m.?
In any event, a call to ST's Customer Disservice line might yield
an explanation and perhaps even a solution. 
