if you have not tried.do not talk rubbish here.
I have done that once. You can be at airport aroud 6:40am start from nus by MRT.(the first MRT is around 5:40)
9:30's plane, be there around 8am is early enough, take 6:20's bus 200 from Pgp to buona vista. use about 20 minutes. take MRT from buona vista to changi airport need at most 50 minutes, so 7:45am you are at airport.
Eventhough
u have to get up around 6am or earlier. Thus, that is not convenient.
All I want to say is seldom ppl will take MRT in this case.
The conclusion is what has BABA said is misleading and Gao Xiao. Nothing special. But somebody(sb)'d like to misread my word, then that is not my fault.