Vehicle Insurance Bail Bond

Does anybody know whether a Bail Bond is a requirement for vehicle insurance - Class 1 in my case - in Thailand or is it an option that can be accepted or declined, reduced or increased in level etc.?

Background; I've recently had a renewal quote - for a bike - and despite earning a 20% NCD, my overall premium ROSE by 30%. This was entirely due to an unrequested and unwanted Bail Bond increase from 600,000 > 1,070,000 THB - that part of the premium rose by 67%!!!!!. No change in the pretty paltry medical benefits.

Personally, I see little need for a BB and certainly not one for 1,070,000 THB. My car insurance with the same insurance agent - Roojai - was renewed in January with a BB of 300,000 which is far more reasonable. If 300,000THB is OK for a car, it should be OK for any vehicle or are we likely to be seen as more of a bail risk simply for riding a bike?