Hi Friend,
As through your Pseudo you should be near my age -53, already- ...I'ld like to help you and avoid you to make too much mistakes.
Importing bikes in Thailand is fully possible, but when done at a private title, it is really a headhacke and it's time and money taking. I would describe the case of a brand new motorcycle.
Just import the bike through a serious forwarding agent with the accompagning invoice from the motorbike dealer where you bought it, with all relevant property and technical papers go to the Ministry of Industry in BKK, explain your case and situation before the bike reach Thailand in order to obtain the Import License every vehicles need to enter into the Kingdom (you'ld need to have a resident address in Thailand or use your Thai wife one's, the bike will be under her name) .
With the Import License, go to the Thai Custom, preferably with your forwarder, clear the bike by paying duties (roughly 70 % of the CIF value with no VAT).
With the Import License and the receipt from the Thai Custom Autorities, return to the Ministry of Industry and apply for a homologation check for registration (beware of the pollution tests). It cost around 30.000 TBH.
After you have passed this, go with your approval receipt and all other papers to the plate number delivering Body, you'll receive firts a copy of the registration book and around 3 weeks later you'll receive your registration book. It cost as well...
Anyway, this is fully possible, Administration Staff is skilled and very kind, I did not encounter any special issue but you have to take it cool with politness and kindness, as they do for us.
This kind of operation is NOT interesting money wise as the bike often will cost you more if you do it as a single import but you'll have the pleasure of having imported YOUR Bike....
Roughly calculated, I would cost you plus or minus 50.000 TBH apart from the custom taxe you have to pay to the Royal Custom, but feasible !
I compare the Thai price for a BMW 1200 GS from BARCELONA BMW Official Motorbike Dealer in Bangkok and the calculation of what it would have costed me if I would have imported it by myself, much better to buy it at BARCELONA Garage in BKK, much cheaper and the Service is there.
I compaired it as well for my DUCATI with the Official DUCATI Dealer in BKK and again it was the same conclusion.
But as we say in France, "Quand on aime, on ne compte pas..."
Just an additional information, as far as there is an Offical Importer in the Country, he is oblige to afford the After Sale Service and Guarantee in the same conditions than any other European or US Official Dealers, signal your act to the Mother Company.
Good Luck, Chock dee and Aspirine...
NB: whose bikker will be aournd in BKK for X'Mas ?