Sounds more like around the Siam Square area then.
Anything with an engine over there is taxed per size of the engine. I saw a BMW Mini for $60K US there.
Years ago I knew Swedes down in Phuket would "Johnny Cash" Harley's into the country by mail, one piece at a time.
There are quite a few large motorcycles in Thailand and you can rent them at the tourist spots (mostly Japanese bikes). Outside of a helmet and light jacket - safety goes out the window when you are cooking. I sunburned myself in mild weather up in Chang Mai riding daily.