there is a very simple reason why import cars are so much taxed here, actually quite a logical reason
Rich Thai pay very little income tax, so the only way they can tax the rich and the very wealthy is through import tax, that's the only place they have full control
so a rich Thai doesn't pay much in tax but when he wants to buy a new Ferrari, he is going to pay for that 20M THB Tax due on his income
it's basically a tax on luxury expenses, instead of income, a tax model that has been proposed even in European countries to make the tax system more fair
actually not a bad system, the rich should pay taxes based on their spending patterns, not income patterns