My many many posts as a strong supported of the Pen, my Favorite Hotel in the World, can be found in this forum, and two trip reports of mine can be found in the Trip Reports forum. Among the many reasons I like the Pen is the relaxing nature of the river itself.

You guys are all overlooking at least one walkable destination from the Pen: the food stall known as Little Chinese Boy on Charroennakorn Road. Very good food and very cheap (by Western standards). Plus, I'd count all the stuff on Charoen Krung (New Road) as basically walkable, since the boats will take you across the river and you can set out on foot from there.