MRT is the fastest.
But if you want all-bus, then you can choose any of these, they
will take more than an hour:
1. service 2 to Kallang MRT, transfer to service 985 to Bukit
Batok, transfer to service 66.
2. service 31 to Marine Parade, transfer to service 36 to
Raffles Ave, transfer to service 97.
3. service 45 to Eunos Link, transfer to service 93 to Lornie
Rd, transfer to service 52.
