The US embassy said it no longer issues letters. Nonthaburi Immigration requires it, though. Otherwise (they told me this morning), they will only issue me a 7-day extension and must leave the country (originally, I came in Dec. 8, โ21 on TR visa 60 days and was granted a 30- day extension in Feb.. and, one needs at least 15 days in which to change visa status, such as to Non-O retirement. FYI