It's survival of the fittest. If foreign workers and maids can
survive with such low salaries, you have to be able to do more to
deserve a higher pay. If the salary is too low even for foreign
workers (and remember employers have to pay a levy for them), then
employers will be forced to raise salaries to retain their workers.
Market forces will decide what should be the minimum wage.
Cool, that's why Singaporean vote for the PAP to pay them
millions to do nothing.