On Soi 15 and Sukhumvit, just next to Yong Lee cafe is a great Sikh tailor who calls himself St. Marco. Great tailored shirts for 12USD and packs and bags in the 100-1000b range.
try staying at Manhattan hotel and not getting sucked into that shop. I had to laugh at an earlier thread asking about where to buy shirts. it is near impossible NOT to buy some if staying near that shop.
TG has bought a couple of bags from there and I have bought some shirts. Lesson..... don't buy from the staff. you can always get a better price from owner.