The law is meant to reduce traffic deaths. It does not address passengers riding in the back of pickups,
The new law has flaws. Older cars do not have seatbelts in back seats. Older buses do not have seatbelts. Songthaews don't have seatbelts.
Don't see how this will reduce the highway carnage, it will increase opportunities for more tea money.
There are moments when seat belts become useless, in fact they can be deadly