Police say 14-year-old shooting suspect appears to suffer from psychological issues and had not taken daily medication.

A teenager in Thailand suspected of killing two people in a shooting spree at a high-end shopping centre in the capital, Bangkok, will be charged with premeditated murder, attempted murder and illegal firearms possession, among other offences, police said.

The suspect, who is 14, will be sent to a juvenile court later on Wednesday, Major General Nakarin Sukhontawit of Bangkok police said, adding that officers were having difficulties communicating with the suspect.

Police said the teenager appeared to have suffered a psychological breakdown and had modified a handgun, which was designed to fire blanks, to allow him to fire live ammunition.