I am considering retirement in Nakhon Sawan end of 2020 to live with future Thai spouse , just researching availability of diabetic medicine , insulin /pills available those pharmacy or hospital issue with doctors prescription , and health insurance cover whilst living here, type 2 / with occasion insulin supplement , any advice , recommendations be appreciated

In my experience as a diabetic in Bangkok prescriptions are unnecessary but drugs can be comparatively expensive even from reputable but inexpensive places like SC Drug on Rama 4. I'd pop into SC Drug, they're very helpful and will tell you prices without any pressure to buy. I use lantus insulin and it's a significant cost. The older women behind the counter speak good English.  I can't guess whether there's an equivalent in Nakhon Sawan. As your diabetes is a pre-existing condition it's unlikely you would get insurance cover for it or anything else the insurer would regard as "associated" eg. high blood pressure or high cholesterol

Getting insulin products i Korat is no problem.I use Lantus solo star injection pens,box of 5 cost baht 3,750 also use Glimpride,box of 30 cost baht 830. All without prescription.

Lefty 

As others have said, products are available here but costly. That includes not just insulin but also test strips.

 

It is extremely unlikely that you will be able to get insurance given that you are diabetic. Self-insuring requires at a minimum 1 million baht set aside that can be readily replenished if you are willing t use only government hospital, around 4 million if you want to be able to use private hospitals.