@mendip - I don't know the situation in TH, but in PI, there's no legal issue with homeschool until Junior High (Grade 10, around 16 y.o.). I'm not sure if the kids have to enroll the 2 years of Senior High (Grades 11 & 12) in a physical school.
I have a colleague who home-schooled her kids for a time (she was jobless, the husband was sole earner). To my understanding, the kids had to be enrolled in a govt approved Home School Program (e.g. XYZ Home School Inc). They paid for some fees, got books & materials from the school. She (the parent) administered the tests. They sent the test results to the school. The kids also had a 1x/ month session at the school - to meet other kids and for the teacher to monitor progress. The kids are issued a report card at the end of the school year. The elder kids were able to enter university here. (The youngest kid had to go to a normal school, since the mom resumed work.) The eldest kid has graduated from uni and has a good entry-level job, which was related to her field of study. So in this case, home schooling was OK for them. Hope that helps in some way.