I'll actually planning on getting some new suits in BKK in July, but reading through all the FT 'tailor' threads I thought I might have something useful to contribute to this particular thread for someone's future use.

I have previously had a very good experience getting suits made at the following HKT tailor:

Peter Fashion House
tel: + 66 76 270949

The shop is located just 2-3 minutes walk from the entrance to the Dusit Thani Laguna - in a very pleasant open shopping mall.