Founded in 1998 in Bangkok, and 19XX in Khao Yai, Thailand, St. Stephen's International School (SIS) joined FOBISIA in 2006. 

The school follows a British type curriculum, and offers the International General Certificate of Secondary Education (IGCSE) at both campuses, and A Levels at the Bangkok campus. 

Stephen's International School is accredited with the Council of International Schools (CIS) and the British Schools Overseas (BSO) approved inspectorate, Education Development Trust (EDT).