I just learned that the import Tax/Customs Duties for imported motorbike parts into Thailand is 30% (ouch) plus VAT of 7%. I will need to focus on buying any Honda CB750 parts needed in Thailand from Thailand sellers.
I bought a NOS ignition switch to my CB750 K2 from a Thai seller on eBay 6 years ago. They/He had some Honda parts.
There are some NOS Honda parts available from Thailand sellers but not many and not a very good selection. I did buy the Honda Mirrors from a Thailand Seller at $79 vs US Ebay seller (best price at $67) so in this case paying a little extra and avoiding customs taxes was the best way to go.
From what I have seen both the NOS and Used Honda CB parts available in the USA are the best selection and also best prices. I will still continue buying in the USA but will need to be very careful and plan on cost +37%.