One thing is a little unclear -- is the bike already in Thailand? First post makes it sound like it is, last post makes it seem like you're going to import it. IF it's the latter, you'll have to figure that as part of the cost and potential bureaucratic nightmares (and possibly bribes or fees) with registering it. I just brought my second CB down to Mexico and instead of paying an agent, did everything myself and it was a royal PITA.
That being said, things like rechroming are going to be much cheaper and more widely available in Thailand (or a neighboring country). Vietnam is also a recent hotspot for repop CB (and other) parts, so you're closer and the shipping would be cheaper.
These bikes, once sorted, can also be tremendously reliable with regular maintenance, and regular maintenance is pretty easy to learn (especially with help here) -- adjusting valves, changing oil and filter and plugs, setting timing, lubing, gapping points, etc.
The bottom line is what you're willing to pay and what you think you'll get out of it. My headaches with registering my bike here in Mexico City lasted a couple months and I was getting ready to throw in the towel, but now that it's registered I am having a blast riding it around. And similar to SE Asia, there aren't that many old CBs around. So if you've got the cash to do it and really want to, I say go for it.
I work in Indonesia and Timor-Leste, and travel in the region -- including Thailand (walked across the border from Malaysia to Narathiwat and spent some time in the South, and of course Bangkok). You'll find that there are some places with old bikes -- there are clubs across Java, for example, especially in Jakarta, Yogyakarta and Surabaya, and I've seen a few old bikes in Singapore (where people have the money to bring them in, although I mostly see 400Fs and twins). I imagine if you get it you might find similar groups in Bangkok or even Chiang Mai, but I have no idea (and I'm not sure where you are).
