In a courtyard set back from the infamous Khao San Road scene is the Tom Yum Gung restaurant which specialises in traditional Thai dishes of a surprising quality, given the area. I picked this rice dish cooked in a fragrant green curry broth in which Thai basil featured very postively.
Right opposite the restaurant's exterior patio there's a very smart coffee house and 'dessert cafe' called The Fabulous patronised by Bangkok's laptop-bearing gilded youth. Given that the iPad was yet to be properly released in Asia I was mighty impressed to be presented with one as my menu when I asked to see their selection of iced coffees.
Here's a little clip I found on YouTube which will give you a sense of the retro-tastic ambience in there: