A fun way to travel is to use the river ferries. They run from piers along the river. You can use the larger Chao Phraya Express Boats which have white hulls with red stripes, or private long tailed boats pr the flat shuttle boats with just a few seats. Boats do not stay for long at the pier so be quick but also take great care as they move off suddenly! Fares start at 10 Baht. A good place to try out the ferries is from the Oriental Hotel and from here you can have a good value trip up north.