The thing is that you can drive a foreign registered LHD vehicle in a RHD country under a permit as long as you’re visiting. Think about driving a LHD European registered car in the UK or vice versa. Thailand is no different. The authorities can permit a Vietnam or Burma or even American registered vehicle to drive on their roads for a certain period of time for travel or transit.
The issue here is that Funnyboneman wants to move to Thailand permanently. This involves importing the vehicle. So in addition to paying all the duties and taxes etc. the car will then also need to satisfy Thailand rules to be eligible to register it which would (amongst other things) require converting it to RHD.
This is my experience when looking at bringing my car from Dubai and importing to Singapore.
However, Governments change, laws change and in some countries in Asia (and elsewhere), there exists opportunities to pay a premium for special treatment.
Probably best to investigate further with Thailand consular advice. :wink: