The 60% or whatever %age the customs deem is the amount is on their valuation of the vehicle.
Registration fees vary depending on which plates go on the car. There are diplomatic plates, business plates, Lao citizen plates, foreigner with residency plates and foreigner without residency plates.
A Google search will find rental costs for you. And now you can drive here on your overseas licence.
Another Google search will find out second hand vehicle costs. As an example of costs an average new Toyota Prado 4WD costs around $130,000.00 with taxes and registration.
To be honest forget bringing your car over and get one here.