The address is Excelsior 115/1 at the Siam Heritage Suriwongse Bangrak Bangkok 10500.

Finding a good tailor in Thailand won’t be easy, but it will be possible. Here are my suggestions:
(1) Do not enter any shop that has touts out front. A tout out front is a sure sign of worse pressure inside. They normally get some kind of commission on your deal
2) Do not follow recommendations from taxi drivers or bellboy. They can’t afford tailor-made clothes, so they don’t know quality or value. But they will get a commission, which you will pay in the price of your order.
(3) Select a tailor inside a 5-star hotel. If a tailor shop is dodgy, it won’t last very long in the hotel.
I would surely recommend Excelsior Tailor in Bangkok since they are well established with four branches in Bangkok itself.
Excelsior Tailor is certainly not the cheapest tailor around – but he does appear to be one of the best. I’ve always been impressed with the business ethics of the Sikh community, and this outfit is no different.
It took me two fittings, but I was very pleased with the final result. They have a pile of magazines in the shop, and the style can come from just about any range imaginable from Amarni to YSL. They also do women’s clothes as well. Nice people.

I bought a tailored suit (jacket and trousers, three shirts and three ties), a fitted dress for my sister and a kimono for my mum. That all came to 15,500 baht – roughly £200 which I think is fairly cheap – much less than I would have to pay back in the UK.