This is Thailand: Answer

The answer to what this truck is doing parked on the side of the highway:

Up ahead is a police check point. This truck is stopped about 50 metres before the police check. Behind this truck is about another 5 trucks all lined up behind it. The truck has stopped probably because either the truck is overweight, incorrectly registered or the driver doesn't have a driver's license. The truck will wait until the police check point moves on. This could be an hour, several hours, or even the next day. These trucks will wait, presumibly so that they are not fined. The incomprehensible thing is though that this truck is in view of the police at the check point. It is obvious what they are doing, but the police will not walk 50 metres down the road to book them. This is Thailand.