The single most common planning mistake we see from families moving to Thailand is treating school as a step you take after arriving. It is not. It is the step that decides when you can arrive at all.
Current guidance for international schools here is to apply nine to eighteen months before your intended start date. Top tier schools carry waiting lists of twelve to twenty four months. Certain year groups are worse than others: reception, the Year 7 secondary intake, and the IB Diploma entry point fill first. If your child needs English language support, capacity per year group is tighter again, so early matters more.
The admissions process itself is more involved than most parents expect. For the youngest applicants it is usually a 45 to 60 minute observation session. From Year 2 upwards, expect standardised English and maths assessments (MAP, CAT4 and WIDA are common), student interviews from around Year 4, and parent interviews at every level.
Then there is the money, which is rarely just tuition. Enrolment and capital fees can run to several hundred thousand baht on top of the annual figure, before buses, lunches and uniforms. Two things worth asking every admissions office directly: whether they offer sibling discounts, and whether corporate billing is possible. Both are common and neither is advertised.
One practical tip that saves more than it sounds. Choose a campus within thirty minutes of where you live. Long bus routes are expensive, and on this island they are also brutal in high season.
Families in the Digi Yesmads community who landed well almost all did the same thing: they picked the school first, then the neighbourhood, then the house. In that order.