What type of confirmation letter is required for a 60-day tourist visa in Thailand?

When applying for a 60-day tourist visa in Thailand, individuals may be prompted for a confirmation letter. Experiences shared by others suggest that various responses can be adequate, including uploading a simple document stating 'not applicable,' a copy of their passport, or even personal financial statements like a bank statement, wage slip, or pension letter. It seems there is flexibility in what can be submitted, with many successfully receiving their visas without significant documentation.