Some 70 secondary students from Jian Hua School in Nakhon Pathom's Bang Len district suffered food poisoning on Friday after school lunch.
Twenty-five of the students were sent to Supan Buri's 17th Somdet Phra Sangkharat Hospital suffering from severe diarrhoea, vomiting and seizures.
Teacher Manasawee Phutthapol, 26, said that some 70 students had developed food poisoning symptoms after having lunch and teachers sent the 25 most severely-affected students to the hospital.
Hospital director Dr Suparit Hengkrawit said the students most likely suffered from food poisoning after having two dishes.
As of Friday afternoon, all students were recovering while only one student – a Mathayom 3 girl – remained in hospital for medical surveillance.