Getting into Singapore with a one way airplane ticket turned out to be not too big a deal. Yes, the airline checkin did ask us and we had to show our passive intinery (ie travelagent made up itinerary that didn’t actually book anything) but once through that, immigration was no problem at all. Turns out that it is likely true that the airlines are charged with some gatekeeping responsibility.
We were also worried about SG’s substantial medicine kit even though we did have a letter from a doctor listing every drug but again we walked through the green lane and no problem.
I’d really forgotten how much I hate the immigration customs process and entering a country with a mandatory death penalty doesn’t help.