Bangkok Bank Mae Sot printed out all 12 months of activity and provided a separate signed certification letter of the balance that day. 100 THB. This was for my retirement extension last month.
A big issue with the 800,000THB in an account is that Bangkok Bank told me they have no provisions for beneficiaries should there be death. Thus, you would need a Thai will. Joint account would not work because I think that the 800,000THB would be only 400,000THB for retirement extension purposes.