we don't have recent recommendations but there are a couple from last year here. Hopefully others can chip in though.
Husband got some good trousers made at the tailors in the Marriott Resort and Spa. There are also a lot of good tailors on Sukhumvit Soi 11.

I had suits and shirts made by 'Versaces'........don't be put off by the obvious name rip off!!
The tailors is just over the road from the 'Landmark' hotel in Bangkok. The main guy in there is called Jimmy and he lived in the UK for many years so speaks really good English. They measured me up and had the suits made in 36 hours - and they are superb. I chose the more expensive material - 70% cashmere and the suits worked out at £90 each, I bought 2 suits and he threw in two free tailor made cotton shirts and two silk ties as well. Excellent quality, they are as good now as when I bought them. I would definitely buy again from them.