My first time in Bangkok was also a single night's stay. Hopefully you won't have this song stuck in your head, like I did, the entire trip... Had the same problem the first time I was in Reno (Shot a man in Reno...) and Kansas City.

You're splitting hairs in determining which hotel is best for one night. I'd go with the JW (others will disagree) because it is the easiest to get to from the highway. The others require a little more time on surface streets. The JW is a quick, easy shot once you are off the highway. Plus, it's closer to the touristy things you are more likely going to do with your very short amount of time in the city.

I like the rooms at the Ren better, and others have had great things to say about the FS.

Enjoy your trip!