Grandchild only 2 but parents looking for places prefer NW as they live Nonthaburi,or North Bangkok as they drive to work near lat Phrao, Bangkok for prmary years age 4-11 after which they may send to UK, fees not an issue I think rather reputation and quality.
If current or recent past users/parents or teachers prefer to pm or link to school website.
The option to stay on until 18 be handy also if they don't choose UK.
I've looked here but inside opinion helpful.
The International Christian School looks the closest, do thry like England have to be regular church goers/believers to gain admission ?
10 Best International Schools in Bangkok, Thailand