I recently spent two evenings at the Navalai River Resort and was very pleased with my experience. Check in and out was very easy, and the front desk stored our bags for us on our last day as we weren't leaving Bangkok until early evening.
I found the rooms to be very spacious and clean, with excellent air conditioning (which was impossible to find on the rest of our trip). We did experience a small problem with tiny ants in the bathroom, but as soon as I zipped up my toiletries they seemed to disappear. I was very pleased with the overall cleanliness of the whole resort.
The pool and bar area on the roof was excellent, and a great place to relax.
The hotel itself is situated right on the River, and there is actually a ferry pier directly at the hotel - which was amazingly convenient. A few minutes walk will take you to the heart of Khao San Road and Rambuttri - close enough to enjoy easily, but far enough to not be right on top of the noise!
Due to the Cleanliness and Location I wouldn't hesitate to stay at Navalai again in the future.More