Alternatively, you can take MRT to City Hall, and walk towards Funan. The High Commission is right opposite 中华总商会 along Victoria Street.
You shall get there at about 7:00--7:30 am, so that you will not have to queue for too long. Prepare S$14 dollars, your passport, student pass, recent color photo (if you don't have, you can take from shops next to the High Commission or the PhotoMe machine in the Commission).
You shall get to the High Commission at about 3:00--3:30 pm on the next working day IN PERSON. (You can go there earlier in the afternoon, but there will be too much queueing.)