There is an attendance requirement at all Thai government schools.
The girl I took in couldn't progress to her next year as she skipped too much school.
Yes, it's true, everyone that turns up gets a passing grade during their free government education which ends age 15 (but that's still only 61% of students from 2019 UNICEF study). At that point 66% of the remaining pupils are culled from the schools as unsuitable for more education and those that continue must pay.
Less than 29% of Thai students graduate high school at age 18 (2019 study).
https://data.unicef.org/wp-content/uploads/2022/07/Thailand-Education-Fact-Sheets-2019-EN.pdf