What are the steps and requirements for extending a tourist visa in Thailand during the COVID-19 pandemic?

A user shares their experience of successfully obtaining a COVID-19 visa extension at the Chaengwattana immigration office in Thailand. They report that the process was relatively straightforward, contrary to advice received from the call center, and that no appointment was necessary. The required documents included a standard set with an additional 5-6 page form, and it's noted that the hotel resident registration must be a printed document rather than a screenshot. Overall, the process took about two hours.