The bottom line is that SIA is looking for people who will cost less.
They seem to be hell-bent in not paying over $15000 Sin pm to the highest paid driver. The work is tough and Singapore is an expensive but safe place to reside. The other word of caution in the far east is that contracts mean nothing. They change with the wind and could leave you at a lurch.
The race in SIA is to squeeze till you bite, then operate at that level to max their returns.
Also at present, the airline is being micromanaged by the government, so the SQ management are just running the office boy stuff daily. Good Luck