u should:

1) make police report at a polic post; if u are in NUS, u can go to NUS NUH emergency where there is a police post; they will give u a report
2) make an advertisement on LiHeZaoBao to announce the loss. Find their number from zaobao.com
3) bring original and a copy of 1) police report 2) newspaper which has your announcement of loss to the China embassy, and ask for new one. It may take $70 and 1month.
4) go to SIR to update