Why isn’t it a very good idea to buy a second-hand car in Thailand ?
Quite simply because of the frequent floods that affect a large part of the country every year.
Often these last only a few days, but many vehicles are completely or partially submerged. 
They are then dried out, restored and put back on the road.
But being submerged can leave serious lasting damage.
And it is very difficult, even when going through a garage, to be certain that the car you’re interested in – which may sometimes be on offer at a very attractive price – isn’t one of those that has been completely submerged.