I am wondering is six hours enough time to go into downtown Singapore using the MRT have a quick look enough and be back at the airport in time for my onward connection.

I am travelling home from Vietnam through to Adelaide Australia and have six hours between flights

I am travelling on New Years Day

Flight Details are listed below:

Singapore Airlines SQ 175 From Hanoi arriving 5:55pm

Connecting onto:

Singapore Airlines SQ 269 to Adelaide departing 11:50pm

I am through checked from Hanoi through to Adelaide so won't have any luggage with me except for carry on bags and have taken the time it will take to clear immigration into account and how long MRT takes into Downtown Singapore into account

Any help would be most welcome