A residency letter, also known as a Certificate of Residence, can be obtained through the Immigration Office in Bangkok, especially if you have completed a 90-day report there. Alternatively, if you haven't, you can request it from your embassy, such as the US Embassy, which provides the letter for a fee of $50 and delivers it the same day. In contrast, obtaining it from the Immigration Office in Bangkok may take up to three weeks by mail, but costs only 200 baht.
90 DAY REPORTING RESOURCES / SERVICES
Use the trusted Thailand 90 Day Reporting Service to get your in-person report done and mailed to you for as low as 375 THB (even if the online system doesn't work for you).
For immediate assistance, contact Thai Visa Centre directly via LINE at @ThaiVisaCentre or Email them.