
Siripong Karnjananivit, 40, made an appointment with police at Channel 9 tv station, saying he wanted to surrender before the camera.
Police then met him at the tv station, where he confessed that he shot to dead his girlfriend; Sunun Srisuwan, 38, and Makino, 5, her son who was born to a Japanese father. The bullet also hurt a girl, Pitchaya, 13.
He claimed that he did not intend to kill Makino. He was in the state of confusion when he dismember his body.
Body of Sunun was found on Sunday in Pathum Thani's Lat Lum Kaeo district on Sunday.
The boy's gruesome body parts were found in an abandoned house in Bangkok's Taling Chan area on Monday.
Initially police believed that the boy was a Korean.