Police have arrested a suspect in the murder-robbery of a gold shop in Lop Buri two weeks ago, in which a young child and two adults were killed.

The suspect is the director of a school in neighbouring Sing Buri province, according to media reports. 

Deputy Prime Minister Prawit Wongsuwon said on Wednesday morning the man had confessed, and said he acted alone. 

The suspect is accused of the gold robbery at Robinson Department store in Muang district of Lop Buri on Jan 9, when the robber shot dead three people - including a two-year-old boy - and wounded four others.

National police chief Pol Gen Chakthip Chaijinda confirmed on Wednesday afternoon that a suspect was arrested and was being interrogated. The suspect was definitely not a scapegoat, he said.

Although people were angry about the crime, they should not consider taking violent action against the suspect, who had already entered the justice system, he said.

Media reported that the suspect was the newly-appointed director of a school with about 40 kindergarteners and primary pupils in Sing Buri province, not far from the crime scene in Lop Buri, and a gun enthusiast.

The 38-year-old man had a master's degree, was married three years ago, and showed no signs of violence around his colleagues.