We see many posts on here asking about how many days can I stay in Thailand on visa exempt or tourist visa entries.
The fact is that there is no maximum number of days that you could stay.
There is a rule that land border entries using a visa exempt entry is limited to two per calendar year (Jan 1st to Dec 31st) but no set rule on air entries.
Any “limit” is determined by the immigration officer you hand your passport to on entry. It’s their decision. If they think you are trying to “milk” the tourist visa or exempt entry system then they can ask you to show proof of an onward ticket, proof of accommodation and 20,000 baht (or equivalent ) in cash.
Very few would be asked for any of these. They’d generally only ask if they are looking for a way to deny you entry. But you *could* be asked.
Some immigration officers may spout a rule of “maximum 180 days in Thailand” or “only 3 entries per year allowed”. That’s just not the case and there are no rules pertaining to those conditions.
A number of local consulates around the region will limit you to one tourist visa per year, but there’s nothing to stop you applying for a tourist visa from a different consulate.
There’s many people that enter Thailand an extensive number of times per year for legitimate reasons (family, marriage, work overseas, etc). There is no limit. But the immigration officer has control over whether they let you enter or not.
Very little recourse if they decide not to let you in. You’could ask for a supervisor but chances are slim that they’d be overruled.
99% of tourists will never be asked for this, so those of you that have been coming for 20+ years will never experience the questions (and possible rejection). Those that the immigration officer thinks that they may be working or milking the system may be.
TLDR : Answer Summary
The duration of stay in Thailand on a visa-exempt entry or tourist visa is primarily determined by the immigration officer upon entry, rather than a fixed maximum number of days. While land border entries are restricted to two per calendar year, air entries do not have a specific limit. Questions may arise regarding proof of onward travel and financial capacity, but most tourists are unlikely to face such inquiries. Local consulates may have their own restrictions on tourist visas, but it's possible to apply for a visa from a different consulate. A recent comment highlighted the importance of being aware of tax residency laws, which consider anyone spending more than 180 days in Thailand as a tax resident.
