The TM30 form is an immigration requirement. The law governing this form aims to ensure transparency in the accommodation details of foreigners staying in Thailand.

It must be completed by the landlord of a property to report the stay of guests within 24 hours of their arrival.

If you are simply coming on holiday to stay in a hotel you won't need to worry about this requirement. Generally this is only relevant to the following people:

Those staying with a Thai friend
Those staying in any type of unlicensed (as a hotel) property
Those who own a home in Thailand (and reside there)
Those who co-own a home in Thailand (and reside there)

TM30 Requirements

To report your stay, you'll need the following:

Copy of your passport’s photo page
Copy of your passport visa page
Copy of your departure card

The landlord will need:

Copy of his/her title deed
Copy of the rental contract

Remember: each time you visit Thailand a TM30 needs to be filed, because your arrival number will change.
Also note that the TM30 is not the same as 90-day reporting. Though you may be fined if you go to do your 90-day reporting and a TM30 hasn't been filed since your arrival.

If you are going to register in person at an immigration department, you can download the Application Form here.

Online Registration

The good news is that neither you (the home owner) or your landlord need to fill out a form or go down to an immigration office. You can report online, when it works, that is!

Most hotels and registered businesses use TM30 online reporting.
Online registration is available here.
You need to first request a username and password, and then log on to register.

For more information, please go click here to access Immigration Bureau Website.

More Sources:
https://www.thethailandlife.com/tm30-guide
https://perfecthomes.co.th/tm030-registration-thailand/