Which guests need a TM30 and which don't

The principle

Section 38 of the Immigration Act B.E. 2522 applies to housing “a foreigner who has been permitted to stay in the Kingdom temporarily”, and a “foreigner” in this law means a person who is not of Thai nationality. So the key questions are: is the guest Thai, and is their permission to stay temporary?

Must be filed

• All tourists, whether visa-exempt or on a tourist visa
• One-night guests: the 24 hours run from arrival. There's no exemption for short stays
• Children: there's no age exemption. File every child travelling with a family
• Long-stay visa holders, such as work, retirement, education or marriage visas, which are still temporary stays
• Border pass holders from neighbouring countries. Chiang Rai Immigration has fined a house owner for not reporting a Myanmar national staying on a border pass
• Foreigners staying with friends or family: the house master must file, even if no rent is paid

Don't need to be filed

• Thai citizens
• Dual nationals with Thai nationality, because they are not “foreigners” under the law. Ask to see their Thai ID card or Thai passport as evidence

Cases to check with your local immigration office

• Permanent residents: Section 38 refers to foreigners with temporary permission to stay, so permanent residents are not directly covered by its wording. Practice may differ between offices
• Diplomats: Section 15 exempts members of diplomatic missions from “the duties of foreigners”, but TM30 is the host's duty, so it's unclear whether the exemption applies
• Foreigners living in a condo they own: there is no separate host. Many offices ask the owner to file themselves. Ask the office responsible for your area

If in doubt, file anyway. Filing when you didn't need to has no penalty, but not filing does (see TM30 fines).