Please have a look at this review and seriously go visit the school. Meet the teachers, meet the admin, look at the daily curriculum and how it is taught.
I really believe you have to go to one of the top tier international schools to get the education for your child you are looking for.
"Worse are those “bilingual schools” where English is thought by underpaid (i.e. THB 15’000/month) Philippinos and the rest is taught by Thai teachers according to a Thai curriculum. The kids don’t learn English and if so, speak it with the same terrible accent while most teachers are more focused on pleasing the parents on what/how good the child was/behaved today at school. A prime example was Hastin Kindergarten in Pattaya; it took me less than six months and a couple of times me picking up the kid to realize that this is the wrong way to go.Read More at: https://move2thailand.com/question/which-international-school-is-worth-the-school-fees"