How long does it take to receive confirmation for a 90-day report submitted via post in Thailand?

The post discusses the experience of a user who submitted their 90-day report via recorded mail and inquires about how long it typically takes to receive a confirmation slip back. Several commenters respond, indicating that the process can take up to a month and that delays are common, especially due to a backlog at immigration. They recommend keeping the EMS receipt as proof and mention that the location of the immigration office may also affect processing times.