I got a custom cashmere suit in Thailand, while I was there on vacation. I got myself measured on my 2nd day in the country, went through a couple alterations, and picked up the suit 12 hours or so before my flight home.
It fits well and I've worn it to 2 weddings so far, as well as a family function. Love the fit and how it looks, although the pants do seem to not be quite perfect. Still a lot better than my old suit, which didn't fit nearly as well.
Anyway, there are many suit scams in Thailand, you've got to be careful.. You can easily get ripped off. I'm not 100% convinced that I wasn't, I probably overpaid.. but the fabrics seem to check out, the assembly seems to have been done professionally, and I would have had to pay a lot more to get a suit like that here in Canada.
Initially they quoted me $700, but I talked them down to just over $400, with 2 stylish shirts and 4 silk ties thrown in. (This is how negotiation started.. "I can offer you this for $700 sir".. "I was hoping to spend something a bit closer to.. $100" - the art of the haggle is a very fine one).. I drive a hard bargain, but the guy who I was negotiating with was pretty good too. I am pretty sure I overpaid, but I think it was a win/win for both of us, so in the end, I don't mind contributing a bit more to the local economy, assuming that the product checks out and I'm still getting a good deal, from my end of things.
Anyway, I would be hesitant about these online places, unless they get good reviews. But watch out for those too.. Basically - do a lot of research before you buy.