Hi jules, welcome to the forum.
My understanding is that most tailors keep a good stock of various materials. If they don't have in stock what you require, they can normally obtain it from Bangkok within a day or two.
The only problem you might find is the choice of colours available. If it's a specific colour you like, and you can obtain it easily where you are, then bring it with you just to make sure.
There have been a number of threads and posts already regarding members recommended tailors regarding quality of work. Just do a search for tailors, something will come up.
