Wat Ratprakongtham is not easy to find - even some of the tour guides and boat hire people look at you blankly! It must be possible to get there by taxi but I recommend hiring a longtail boat for a couple of hours. If the driver doesn't know where to go either try another one - or risk the following directions. Take the Klong Bangkok Noi (past the Royal Barges) and keep going for about 45 minutes. Keep straight on or right at junctions. The temple is on the left! It is worth it, especially as almost no one else goes there. The Buddha is huge and the temple worth seeing.