If that is the main difference then for Thailand seems logical to stick to Class 1

Have number 1 insurance for a Isuzu twin cab in it's third year 13,800 thb for 650,000 thb coverage.
Hope I never have to claim the top amount for a written off car. I may not be here for the chequee handover.

Insurance shop is as your approaching Nong Samrong markets on the left, almost first shop you come to.
Name is in Thai.

Another little thing to watch on your insurance, is the value attributed to the vehicle, which is usually nowhere near the cost of replacing "like for like".
If the vehicle is stolen, reported to police, not found, and paid out on, it is then the property of the insurance co when it is later found.
Not sure how true it is, but I was told by the salesman at the insurance company a few years ago to go and check the police station car park for the car, as after a certain time the police are entitled to a percentage of the value when returning stolen vehicles to the insurance company, and they "may not get round to doing the paperwork required" until after this date :-"

what you also can do is named driver(s) , in my case 1 driver which is cheaper than 2 or more drivers ,
as my wife doesn't drive the car ....