You appear to be asking about a 30 day visa exempt entry since a visa on arrival is only for 15 days after paying a 2000 baht fee for it.
The 30 days starts on the day you enter the country.
Show both bank books when you apply to show you maintained the 800k baht. Just be sure there is only a short period of time while the funds are being transferred.
Unless you are 50 years old or over now your only option may be a a tourist visa to stay until you can apply for a non-o visa for retirement anda one year extension.
A multiple entry tourist visa (METV) might be the best choice.