A friend of mine owns one of the better shops in Bangkok. I asked him the very same question. He smiled and explained that it is all about

• getting customers at the beginning
• doing lots of mailorder

and it is all about margin. They subcontract plenty of their work to sweatshops but run an own workshop with five little Indian tailors. They pay about 8000 Bhat each a month plus certain bonus' for the work done of 100 to 400 Bhat for a suit or 10 Bhat for shirt. I really do not want to know what the pay to the sweatshops. So remember what you pay for your suit, what the fabrics cost and soon you will know that running a tailorshop in Bangkok (not: being a tailor in Bangkok) is one of the better jobs you can have there.