The purpose of having 800,000 baht in an account is so you have funds, if required, for emergency treatment.
For a bank to decide to have access to these funds frozen is totally against the reason why immigration want a foreigner to have a considerable amount available at all times.
Requirements in Thailand by different organisations seem contradictory at times.
Another example is organising an O visa and having a bank account - the old chicken and egg dilemma.
Am aware it's not cheap @ 650k baht ( more like 10k for 60 months ) however application is simple, is no upfront deposit held requirements and is my call on health insurance.
Other upsides are that I am only charged if the visa is approved, and I get to pay for after approval
At met at Swampy immigration by a special elite department officer and given
Letters of introduction to bank and for drivers and riders licences.