Here is the latest official announcement from immigration due to the Covid 19 virus regarding Visa Amnesty rulesVisa: no further extension after September 26th. 1
People with a tourist visa (TR, TS, VOA) must have left the country by September 26, 2020.
Exception sickness: A medical certificate must be presented to the Immigration Office.
Other exceptions: No flight available or there is an "outbreak situation". To do this, you have to pick up the exceptional situation from the responsible embassy (e.g. German embassy in Bangkok) and present it to Thai immigration. The extension may apply for a maximum of 30 additional days. [it is unclear what is meant by -outbreak situation-] [it is unclear how to prove that no flights are available]
Long-term visa holders must apply for an extension due to the need for each type of visa. Note: An application for extension must be submitted to any local immigration office by September 26, immediately. All types of visa extensions apply from September 27th.
Notification of residence. A 90-day notification with a due date from March 26 to July 31 must be sent through certain channels from August 1 to August 31.