I'm pretty sure none of the other Honda dealerships in CNX are allowed to sell anything bigger than 250. I bought my cbr250r from Nat Honda on Huay Kaew Road and asked them if they could get me a cbr650f ... they sent me to Big Wing.
For what it's worth, my experience at Big Wing CNX, 2 weeks ago, went as follows: the salesman was very pleasant, but was only able to offer me 45,000 baht as trade-in on my 2-year-old cbr250r, which I naturally declined. I then investigated the finance possibilities: I could have obtained at least 50% finance, even as a farang, but I found the interest rate of 9.2% punitive.
In the end, I bit the bullet, brought more cash over from the UK and laid down the full 300,000. 3 hours later, I rode away on a brand new cbr650f.
I won't pretend that financially it wasn't a painful decision, but after 600Km, it feels fully run in and, more importantly, is easily the best bike I have ever owned, so I feel vindicated. Nevertheless, I will not be entrusting it to Big Wing CNX, even for its first service, but will take it to Nat at the Piston Shop.
Good luck with whatever you decide.