A gunman killed at least three people in a shooting next to a school in Thailand this morning.

The alleged killer opened fire at a house next to the school in Suphanburi province at around 9am local time.

Officers shepherded hundreds of pupils and teachers into safe rooms as they locked down the area while tracing the suspected attacker.

They said two women, Ramphoei Jaiboon, 67, and Chatarat Suphab, 51, along with one man, Somphas Jaiboon, 51, were killed. At least one other victim was seriously injured.

Officers surrounded the house for around 30 minutes before charging inside, but did not find the suspect. They fear he has escaped.

They said the attack was around 50 metres from Wat Yang Sawang Arom School, prompting teachers to bring pupils inside buildings for safety while officers guarded the area. They believe the suspect's son also studies there.

Police said that students are safe and should remain inside buildings, protected by six police officers.