I can confirm, its definitely legal in practice to use. I just stopped by SG on my way home from a long business trip. I am not afraid of the government on these short visits (when I am there for a couple months at a time for work, its very different). I checked with my law firm there, the worse they can do is fine me, so I decided to go for it.
I experimented on my shopping day, wearing a Philippines T shirt (so it was clear I was a tourist so as not to get local vapers into any trouble). I vaped everywhere. I was in Sim Lim and then everywhere on Orchard St. and the high end tourist shopping areas. I was stopped by guards many times, explained myself, and was just told to stop doing it in-doors. I was accosted twice by police and told I have to confine my usage to smoking areas. That was it. I, obviously, won't be doing that ever again, I just wanted to experiment.
