I would venture further off than Khoa San rd., to see more of the city and get away from 'farang-land' if nothing else. No specific recommendations, but if you happen upon a tuk tuk driver you like, try to swing them into the deal as well: they get 'gas vouchers' from various tailors and gem salemen for bringing farang to their shops. If you actually buy something, they get more - so if you know you're buying, try and convey this to them, they may get set up and give you their # to become sort of a regular driver while in town, for cut rate prices. I had this arrangement with a guy, 'Sey ten', even though I didn't buy big, I had time, let him take me to several places where I feigned interest just for the vouchers, then he would set me up whenever he could - plus it added to my hilarious and appropriately BKK deboucherous slogan: 'Satan is my tuk tuk driver'. I'm still thinking about having bumper stickers made...

Hello folks
I have a friend that lives in Bangkok and he uses Savile Row Tailors on Suriwong road. He and his colleagues use this tailors for all their business suits etc
I am traveling to Bangkok in December and will be using this tailor when I arrive; I have used them so I can guarantee their quality of work. As for price
I could say reasonable
Hope this helps
Joseph

With over 100 Tailors shops in Bangkok it was rather hard to choose the right one while staying in Bangkok.

DO NOT enter any shops that you are taken to by guides - you get ripped of as the guides get commission. Tuk Tuks and taxis also take you to guide shops - it is better to call the tailor you are interested in yourself and they will recommend you how to get there.

I have used many tailors in Bangkok and have been totally impressed with Excelsior in downtown area.
A must visit shop by the delegates and embassy staff in Bangkok.
Their service is outstanding and they treated me and dressed me like a King. I have now made over 10 suits and 50 shirts with them in the last 2 years and am extremely happy with them. They visited my brother in law in Germany also on their visiting tailor trip and all his friends were also happy so if you need a suit made - don't waste your time - go to Excelsior.
Excelsior tailoring entails the personal attention of a cutter who measures the customer, creates and cuts a pattern, and directly supervises the making and fitting of the garment. They also use English finest fabrics and trimmings.
Visit them at excelsuits.com Good Tailor and reasonble price.

Probably too late for this too, but while I was there, I was at Crown Tailors in Sukhumvit Road soi 8. An excellent tailor in my opinion. Very helpful and patient throughout the process.