I went to Imperial World on Lad Phrao (Big C, Lad Phrao) for to get my Non-B today.
What a nightmare. If I hadn't had the company fixer with me, I'd have been fucked.
The immigration bureau there normally handles only Burmese, Cambodian and Lao workers. Judging by the incredible masses of humanity gathered there, it must be the only place in the whole of Thailand that takes care of these workers.
Now, add the Chaeng Wattana crowd of tourists and expats needing services in an area that is about the size of the downstairs area of my townhouse.
Luckily for me, the fixer got there early and wasn't hesitant at all to jump the queue. It took about an hour and I was out of there. However, in the hour that I was there, they had only called NINE queue tickets to the window.
Another thing to keep in mind is that this branch has different hours than Chaeng Wattana, 10:30 - 18:30, but they start giving out queue tickets early. I got there at 9:30 and my fixer had already gotten my ticket.
Hope this helps!