This is a map of actually two rides that I did, one on November 5, and then a second on November 6th. I have all kinds of photos embedded into the map, so you can see what you would be riding past if you did this. Day one was mostly east bound and back on some large arterials; day two was a more pleasant and scenic ride to the river and the Grand Palace.
View Bangkok flood bike scouting in a larger map Pier on the overflowing Chao Praya:
The most famous Khaosan Road, photographed from Samsen Road: