FYI re submiting TM30 via registered mail in Bangkok.

I've sent the TM30 form (together with a signed copy of my passport, a signed copy of the blue book for my condo, a stamped envelope for returning the receipt) on 13 Dec via registered mail.

I received the receipt from immigration office by mail today (or could be earlier but I haven't checked the mailbox for the last 10 days). So mailing in the form really works!

Here is the address stamp from the immigration office for TM30.