@Br***
the informal rule of thumb for air entries is if you are in Thailand more than you are out of Thailand. 90 days in 180. For land, it's 2 without a visa per year. For embassies, they'll look at your history.
I get the 90 day in 180 is not law. But it is a rule of thumb they use and it is repeated on both official embassy websites and the Ministry of Foreign Affairs:
"Furthermore, foreigners who enter the Kingdom under this Tourist Visa Exemption Scheme may re-enter and stay in Thailand for a cumulative duration of stay of not exceeding 90 days within any 6-month period from the date of first entry."
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If they were actually to formalize this, and have it as a hard limit (like Europe/Schengen), a lot of people would probably be very upset, it would be less flexible than it is now, where it's only a rule of thumb- people can still do a land bounce now, for example, and that's pretty reliable.
As it is now, if you try the sort of in out staying a long time somewhere like the UK, even as another Westerner, you'd probably run into issues. Plenty of stories of Americans being denied into the UK because they were just there a little too much. They have discretion, and it's not a hard rule either.
People who are keeping it under the levels that would be acceptable in a Western country are very unlikely to have issues. OP, who sounds like a first time traveller, is virtually guaranteed to have no issues.
It's people who are pushing it to the limit that have issues... but at least in the current system they have the option of trying it. If they formalized this, it would likely be more restrictive than the informal cut-off they apply now (and not to everyone).