Importing a motorcycle can be an expensive experience.
The import duties and fee's to get the motorcycle in to Thailand will probably end up as high as 187% of the value of the motorcycle.
To get license plats for your motorcycle, so you can ride it legally on the road you need first, if the motorcycle model is not known in Thailand, your motorcycle needs to do a “exhaust emission and road safety test”, what cost roughly about 45,000 Baht.
It is possible that your motorcycle fails the exhaust emission test, but passes for the road safety test. For this you can change the exhaust pipe, adjust the fueling of the motorcycle and do the test again, this will cost about 20,000 Baht.