The wooden bridge in Sangkhlaburi crosses the lake in between Sangkhlaburi town and the Mon side. It is the longest wooden bridge in Thailand and also rumoured to be the 2nd longest in the world!
Not only is it a beautiful place to go to watch the sun rise and set, but at these times of day, the bridge really comes alive with people walking to and from work, vendors selling food and other items and kids playing. When the water level of the lake is high enough (usually between November and January), you often see children jumping off the bridge and into the lake beneath.
If you make it to the gorgeous town of Sangkhla, the bridge has to be a priority during your stay - I happily spend hours down there watching the world go by with my camera.