The pay is dependable on how the job title of "Engineer" is been used.

Most singapore engineers are considered as merely highly educated technicians.
Local university engineering graduates are products from a mass production factory (NTU and NUS)to support the industries. We (I was an enginner in this area too) do not think, we do only. So a pay from $2.5k to $5k is the norm.

Some overseas educated engineers and few local engineers could be better as they can think and do. Those with this "think" factor normally are rewarded with higher pay, at least $8k and above.

Richard is right. Read for new knowledge is important!