I will NEVER pay for insurance here NEVER a total waste of $$$ they will find any excuse possible that is just the reality here in Thailand and about anywhere.
One of the numerous reasons I avoid most NOT ALL foreigners here like the plague. Too many with very shady backgrounds just wander right on in. It has been going on for decades.
It was never your mistake. The only mistake you made was the location. But even in Nakhon Nowhere being able to speak Thai I was still forced to pay a bribe for no good reason. The only reason I allowed it to happen was lack of time to argue and my family. Otherwise I would not have hesitated to just walk away and apply elsewhere. More than once I had them play a stunt at a certain border. A warning for everyone double and triple check your visa stamp when entering. Sad they are still doing the same B.S.