Police are examining a pair of shorts and the contents of its pockets to identify a rapist who allegedly assaulted 10 elderly women in the provinces of Samut Songkhram, Samut Sakhon and Nakhon Pathom.
The shorts were discovered at the home of the third victim - a 61-year-old woman in Samut Songkhram's Bang Khonthi district. Other than semen, police also found a piece of wood, nylon fibres and the remains of a bug in the pockets.
Crime Suppression Division deputy chief Pol Colonel Kornchai Khlaikleung said the piece of wood could indicate that the suspect worked with trees, while the nylon fibre could suggest fishing activity.
The shorts also look like something that people wear at home, so it could mean that the suspect lived in the area at that time, he said.
He added that the attacker might be about 173 to 175 centimetres tall judging by the 26cm footprints found in the area, which also meant he had been scouting the area for several days before attacking the victim.
In Nakhon Pathom province, police are checking footage from 12 security cameras for clues and are asking provincial administrative officials to help compare fingerprints at the victims' homes to those of the 100 recently released convicts in the area.
In the province's Sam Phran district, where some 30 elderly women living alone might be targeted, police officers have been dispatched on patrol boats down the Tha Chin River and canals from 10pm until morning daily.
The patrol boats were also present at Buddhamondhol and Nakhon Chaisi districts.