Check their location before you go. They did have a shop right across the Chao Phraya in Bangkok Noi. They have a new one out in Nakhon Pathom fairly near Putthumonthon on Sai 3 - if you go straight out that way over the Pingklao Bridge, you can turn left on Sai (not Soi) 3 before you get to the turn to Putthumonthon. There is a map on their web site, though it is not really to scale.
A little English is spoken, but if you want to discuss subtleties, be prepared to use Thai or bring someone along who can. I went out to look at the W650, but it had been sold the previous day.
My Thai friends say that their prices are high, but on the other hand they claim that they can get real green books in 3-5 months. After some months of searching, if you are looking at anything other than HDs or BMWs, there's a very high likelihood that you are looking at a doctored green book. That's true whether the seller is Thai or farang (the difference being that the farangs are often unaware of the irregularities in their documentation, or think that it is "normal".
I don't find their prices any worse that some offerings in this group, and with some solid references they may provide a viable option for mid- to big-bike buyers. They have an above-average interest in "classic" style bikes, like the W650 and SR Yamaha thumpers. Check the web site...
http://www.dbigbike.com/index.php?optio ... &Itemid=28