Are we discussing extensions to an existing visa or a new visa which is what I read. It's important to be clear for the benefit of first timers wanting to retire to Thailand.
It's THB800,000 OR THB65,000 per month. However, you have to show that the money goes in every month for 12 months to qualify. If you elect to put the THB800,000 into your account, it must stay there for 3 months prior to the application and 3 months after the application.