I know the main market is on the weekend but do they have some stalls there normally? If not can someone recommend another good Bangkok market?

After a normal market, copy goods etc not fruit and veg

There's a section at the back, accessible from a street roughly parallel with the main front road, that sells mostly furniture, art, and pet supplies, but not the 'usual' market things.

There's an MRT station right there but I can't recall the name. There are also MRT and BTS stations at the front, but a long walk around to the back.

Pratunam may suit your needs better on weekdays.

http://www.bangkok.com/pratunam/pratunam-wholesale-market.htm

http://www.bangkok.com/shopping-mall/mbk.htm

The main market in Chatuchak also opens on a Friday, but many of the shops do not open or open very late. Best days are Sat and Sun from about 10.30 am

There is a plant / landscape market open on Wednesdays too - Been a while since I have been so I may have the day wrong.

There is a plant / landscape market open on Wednesdays too - Been a while since I have been so I may have the day wrong.

It's open on wednesdays and thursdays.

The MRT station is Khampang Phet (excuse spelling).

Only Chatuchak Plaza at the back is open weekdays but they only sell household, best bet is to go to Pratunam Market or maybe Sukhumvit in the evening.