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.