like all insurance companies world wide they will always be reluctant to pay out, but in my experience if you are honest and transparent with them they will pay out what your policy entitles you to receive. I have Pacific Cross and I claimed last year, off course they investigated, but they eventually paid out.
The 800,000 baht must remain in your account 3 months after you receive your yearly extension and also 2 months before you apply for your next yearly extension. You are correct the balance cannot drop below 400,000 baht at anytime throughout the year, so basically 5 months must be maintained at 800,000 and 7 months you can access the funds if you wish.