General Itthiphol Piriyapinyo, deputy commander of the province's police, expressed scepticism over Anuchit Lamlert's confession.

Anuchit was being held in custody and continued to insist he murdered the tourists after an attempted robbery went wrong.

"It could be seen from the re-enactment that he was skilled with a firearm. He shot like a gunman, without touching the victims' belongings. It contradicted his confession," Itthiphol said.

"So we will re-start the investigation from when the two Russian women arrived at Utapao International Airport, checked in at a hotel and spent eight days in the Pattaya area."

Tatiana Tsimfer, 30, and Liubov Svirkova, 25, arrived in Thailand with a Russian tour party on February 16 and were shot dead by a Thai man at dawn as they sat in deckchairs on a Jomtien beach on February 24.

He said either woman could have had personal or business disputes in Russia, which could relate to international crime.

Officers said both victims' mobile phones showed they had called Russians in the area and in their motherland during their time in the Kingdom. Officers will investigate the victims' relationship with several Russian men in Pattaya.

"We have too little information about the victims so we must wait for more details from the Russian Embassy about whether they had any known disputes," Itthiphol said.