If you are require lots of mobile data on the move, you might consider getting this 7 days Tourist SIM from M1. Each card comes bundled with 100 GB of data that lasts you 7 days. It also comes with 100 SMS and 500 minutes of local calls. It also throws in a 20 minutes of IDD calls.
The good thing about such a card is that you do not have to activate it immediately after purchasing it. With 4 cards, 4 x $15 = $60. So, you get 400 GB of data for one month. This is cheaper than any post paid plan out there.
Currently, Zero Mobile offers an unlimited plan at S$69.95/mth. There are two other cards at S$30 and S$50 which I don’t think it is worth it since they only offer 100 GB data for more days.