According to Police Maj. Gen. Achayon Kraithong, the shooting happened on Thursday at the Child Development Center in the Nong Bua Lamphu province's Uthaisawan Na Klang district.
The shooter was a former police officer who later shot and killed himself, according to media reports.
One teacher, two police officers, 22 children, and 26 total deaths have so far been confirmed, according to a regional public affairs office spokesperson.
Although mass shootings are rare, in 2020, a soldier livid over a property deal shot dead at least 29 people and wounded 57 in four different locations.