Damnoen Saduak Floating Market, 80 km southwest of Bangkok in Ratchaburi province, is one of the largest and most popular floating markets among tourists. Also known as Klong Lat Phli Floating Market by the locals, the market is active in the mornings only, from 6.00 am to 11.00 am. If you want to take photos without hordes of tourists, get there early.

Several floating markets ('talaat naam') in and around Bangkok offer the tourist a picture-postcard image of the traditional Thai way of life. Small wooden boats laden with fruits, flowers, vegetables and other produce from nearby orchards and communities make a colorful and bustling scene at market time. The boats are inevitably paddled by Thai women in blue farmer's garb ('mor hom') and flat-topped conical hats called 'muak ngob', which are characteristic to all parts of Thailand. The floating markets are still important commercial centers for those living along the banks of 'klongs' with no road access.

Source - http://www.thailand.com/travel/recreation/recreation_bangkok_floating%20markets.htm