I thought buying sim card in Singapore would be like Vietnam because of management policy, but I was wrong. In Vietnam, namely Tan Son Nhat Airport, you will have many choice in front of Arrival gate which cheaper than in the downtown. But Singapore is the opposite. My boyfriend said we should buy all tickets we need before entering the city, and he bought a Happy sim has data pack 17GB with S$32 and 2 Nets card (train pass) with S$7 per each. I have no idea with Nets card. It was more economical than standard ticket. The problem is the sim. We went around Boat Quay on the second day, got into 7-eleven and saw Happy sim sold for S$15. Then we were just able to look at each other laughing :))
→ If you can, just take Singapore maps for free and discover the city instead of buying sim for internet only.
→ In case you need internet, at MRT or some walk streets such as Chinatown Food Street or shopping malls, drink stores has wifi limited free for you.
Have a nice trip!
(I will update photos later)