What documents do I need to extend my 30-day stay in Thailand on a multi-entry visa?

YES, your believe is correct even when others try to impress you with form numbers

TM30 is just a form number of the form used to register your address.

You do not need it, you need the receipt that the registration is done

Your hotel, if you handed over your passport at check should have made the address registration, go back to the reception and ask the Receipt of Notification which they can print out until 7 days after registration is made.

If you stayed longe, a new registration can be made to get a print of the receipt.

See example

Get a copy of the TM30

PASSPORT with 6months

In addition to the general guidelines

@Tod ********

posted above, you’ll need the following:

TM7

STM/11

TM30

Receipt you paid for accommodation (or) rental contract

This is what I was asked to produce when I did my extension at IT square. I think Chaeng Wattana started asking these first, then IT Sq. practised later.

𝗜 𝗯𝗲𝗹𝗶𝗲𝘃𝗲 𝘁𝗵𝗮𝘁 𝗧𝗠𝟯𝟬 𝗶𝘀 𝗱𝗼𝗻𝗲 𝗯𝘆 𝘁𝗵𝗲 𝗵𝗼𝘁𝗲

@𝗹 **********

�𝗮𝘁 𝗶𝘀 𝗻𝗼𝘁 𝗻𝗲𝗲𝗱𝗲𝗱

Sadly Ben Bennett that is a mistaken belief :(

Most offices now require you have the TM30 receipt (that the hotel can print for you) showing you're registered as staying in the area served by that immigration office

this is the general list of what can be required to get a 30 day extension on a tourist visa or free stamp entry