If you desire to get a suit stitched in Bangkok or anywhere in Southeast Asia, then there are few factors that you must get clear in your mind:
1. Bespoke signifies hand sewed - no machines works. In spite of the fact that every tailor in Bangkok addresses himself as a custom tailor in Bangkok, this is certainly not true. Genuine custom tailoring work requires a good deal of time. Otherwise, it just will not stick up to global standards. Bespoke tailoring generally requires that you spend time working directly with the tailor who stitches, take your fits, design cuts and pattern for your suit.
2. Fabric matters a lot. It is significant to realize that craftsmanship is just about half of the value of a perfect fitted suit. The other half depends on the fabric or material taken in to use. You could bring the world’s best tailors to Bangkok and provide them with rayon / polyester / sheep ass-wool blend pinstripe for stitching suits and you will realize that not a single suit is good to wear. This is due to the poor fabric quality and also the threads, the interfacing, the lining, etc... Remember before buying a $99 suit that it is impossible to make a well fitted suit in this cost anywhere in the world. A suit made using such crap materials simply can't hold its shape or structure for long.
3. Bespoke or made to measure. Majority of the shops that address themselves as "tailors" are not tailors in real; instead they are merely material salesman. Such shops just take your specifications and fittings for passing them on to actual tailors who do the real tailoring. Thus, what you are receiving from these are not bespoke tailors, but "made-to-measure" which is entirely a different class of tailoring.
4. Time counts. It does take time to provide a well fitted suit for you. Providing a bespoke suit demands time for shaping, pressing, remolding, sewing, etc... There are also various other essential fittings prior to a final delivery. The minimum turnaround time at a proper tailor is 2 weeks in general.
5. Design sensibility. Many tailors have absolutely no design sensibility or if they have one, it is very different from your own. You just cannot rely on a tailor to read your mind exactly and bring forth the suit or any apparel that you really wish to dress in. However, if you can walk into a tailoring shop and can clearly explain that you want a "single breasted three button roll to two button double vested jacket with peak laps, a natural shoulder, high small arm holes, high waist suppression, floating canvas, a patch left breast pocket, angled side flap side pockets, with a ticket pocket on the right side", or a something like that then you might get a suit of your dreams. But, if not, then it can be a problematic situation for you, if you don't know what it means and what you need to get a good suit.