Doctors say food poisoning is suspected after 147 children experienced abdominal pain, vomiting and diarrhoea at a public school in Yasothon on Wednesday.
Some of the young pupils from Thetsaban 3 Hathanwakham School had more severe symptoms, requiring admission to Yasothon Hospital.
Officials said that 38 young students were admitted to the hospital for stomachache, vomiting and diarrhoea and were under close watch by medical personnel there.
A team has begun conducting a thorough investigation of personnel involved to find the cause of the incident.
The children affected ranged from kindergarteners to grade 3. Investigators are examining raw materials, samples from food handlers, drinking water and the school environment at large.
Thetsaban 3 Hathanwakhom School announced it would close on Thursday and Friday for cleaning and disinfection.
