SISB International School (Thonburi Campus)

SISB's Thonburi campus is one of six schools run by SISB Public Company Limited, which opened the original Singapore International School of Bangkok in 2001. It is on Ratchamontri Road in Khlong Khwang, Phasi Charoen district, on the Thonburi side of the Chao Phraya. It opened in 2017 as a nursery and primary school and has since grown into a full school for ages 2 to 18. It serves families in west Bangkok who would otherwise travel to the Pracha Uthit flagship in Wang Thonglang. It is a day school; SISB's boarding is at Pracha Uthit.

Each stage follows a different curriculum. Nursery and Kindergarten use the UK Early Years Foundation Stage, combined with Singapore content and daily English, Chinese and Thai. Primary follows the Singapore curriculum, known for its approach to maths and science. Grades 7 and 8 use a hybrid of Singapore and UK programmes, Grades 9 and 10 lead to Cambridge IGCSE, and Grades 11 and 12 study Cambridge International AS and A Levels. English is the main language of teaching, and Chinese and Thai are taught throughout.

The campus has a swimming pool, an indoor sports hall, a library, a tiered auditorium, science laboratories, art and music rooms, and covered playgrounds for the youngest children. For 2026–2027, annual tuition is THB 401,700 for Nursery, THB 470,700 for Primary 1–2, THB 567,300 for Primary 5–6, THB 609,300 for Grades 7–8, THB 650,700 for Grades 9–10 and THB 789,300 for Grades 11–12. An education resources fee, meals and a THB 220,000 enrolment fee are charged on top; the enrolment fee was being discounted by half for 2026–27.