Located just a ten-minute tuk-tuk ride (about 50 baht) from Chinatown, the Bo-Bae Towers and Market is most easily reached en-route to Sampeng Lane via the National Monument BTS station (five minutes and about 40 baht by tuk-tuk), or on your way to the National Stadium BTS station coming from Chinatown. The Towers is a large, five-storey wholesale clothing and garment complex, consisting of Bo-Bae Towers 1 and 2. On the fifth floor of tower two is the Food Center, a cafeteria where many types of affordable Thai food can be enjoyed. Most garments at the complex are cheap and the type you'd find at small local markets scattered throughout Thailand. Still, there are great deals to be had.

Walking across Krung Kasem Road, which runs along the front side of the city block where the complex is located, and then crossing over one of the many bridges is the actual Boe-bae Market - selling much the same thing, although in a nicer atmosphere. The market consists of four to five city blocks which are surrounded by canals and linked by bridges. Old and weathered yet charming shophouses provide an interesting walk through the markets narrow alleyways. Some shops here close around 16:00 although many are known to stay open until 01:00 or 02:00, depending on business transactions.

How to get there: Take a tuk-tuk or taxi from BTS National Stadium station to the market. All drivers (unless he's just too stubborn) will know how to get there.
Items at market: Mainly cheap garments
Open: 09:00 - 16:00

http://www.hasekamp.net/markets5.htm

We believe that many street market sellers in Bangkok (and maybe even far outside Bangkok) do their wholesale shopping in Bo Bae Tower. Prices are reduced considerably when you buy larger quantities.
Also with private persons, however, this market is hugely popular. One of my sisters-in-law travels once a year from Phuket to Bo Bae Tower in Bangkok and return with a trunk filled with clothes for the whole family