Police yesterday arrested four people suspected of the July 4 rape of a mother and her teenage daughter.

Two men and two women are in custody for the alleged assaults.

The victims claimed they were raped by robbers in the Pathum Thani home of a suspected German underworld figure.

Provincial police commissioner Lt-General Wuth Puawase named the four suspects as Boonyong Khongsiri, 49, his nephew Kosin Khongsiri, 25, the nephew's common-law wife Wilaiwan Pheungchai, 25, and the businessman's maid, Plew Seubrom, 54.

Boonyong was charged with robbery and the rape of the wife. Kosin and Wilaiwan were charged with robbery. Plew was charged as an accomplice, he said.

Police continue to look for Boonyong's son Channarong Khongsiri, 26. He is wanted for the alleged rape of a minor and robbery.

The German's wife alleged that at about 4am on July 4 the gang broke into the Thanya Buri district house, tied her and her 13-year-old daughter up, before raping them and stealing valuables worth Bt590,000.

Wuth said police arrested Boonyong the same day. He told them Kosin and Wilaiwan had fled to Phuket.

Boonyong reportedly confessed to the crimes. He said Channarong had asked for help seeking Bt700,000, claimed to be back pay for working as the German's bodyguard.

He also claimed the man owed him money for abducting another German businessman.

The man was not at home when they arrived. The wife knew nothing of the alleged debt.

The wife and daughter were then raped and robbed.

Boonyong claimed to have an intimate relationship with Plew, who believed him to be a policeman. He wore a uniform whenever he visited. He had been in the house on several occasions.

He told police Plew let them into the house on the day of the alleged rapes and robbery.

Police have been unable to contact the German man.

They suspect he may be involved with an international criminal gang, he said.