Pro Color Lab
As far as I remember a bit cheaper on Lab services than IQ Lab.
And they sell film, which IQ doesn't. And quite cheap compared to european prizes.
A pack of five rolls of Fuji 120 Pro 400H(Used to be NPH) is around 12.50$. He carries Kodak as well. And 4*5 plate film and polaroids and of course 135.
If you need a lot of film call they guy up a month or so in advance to make sure that he can get it for you. He's English isn't immaculate but it worked out ok for me twice.
HOW TO GET THERE:
Take the subway(not the skytrain) to Huay Kwang. Get a motorcycle taxi and tell him to go to Pratcharatbamhen soi 24(the soi is called "Soi Ratchadaniwet"). There is a 7-11 on the corner and an ATM,which is good thing, 'cause if you pay cash Pro Color Lab will suspend some kinda fee. The shop/lab is located halfway around 100-200 metres down the street on the left hand side. The motorcycle ride is about 20 baht.