What are the insurance requirements and police clearance needed for the Thailand Non-OA visa application for British expats?

I just received OA approval. The insurance requirement is an 'or' situation. For me I purchased one year medical insurance from a Thai approved company starting on the day I arrive in Thailand. The entire year coverage is purchased up front. The process was very easy, the Thai Embassy website provided a list of eligible companies and once purchased I received all required documentation within one day via email. I made copies of the documentation including the membership card and brought to thailand. This was important because immigration asked for proof of coverage at entry point entering Thailand. My copied documentation was accepted and I was stamped for the initial year. Hope this helps..

Is there a reason you're applying for the non-OA visa? Normally people want the non-O visa which doesn't have any of these requirements. There are certainly circumstances that can make the OA visa better for some people, but the non-O is what 99% of people actually want.