DNA tests have confirmed that one man is responsible for 10 sexual attacks targeting elderly women.
The repeat offender, however, is still on the run even as police have launched a manhunt covering the provinces of Ratchaburi, Nakhon Pathom, Samut Sakhon and Samut Songkhram.
The latest attack, in which a 73-year-old woman was raped, took place early on Sunday in Nakhon Pathom province.
"Call 191 or 1599 if you have any tip-offs," police spokesman Lt-General Prawut Thavornsiri said yesterday.
Police are offering Bt200,000 (S$8,306) for any tip-offs that can lead to the arrest of the serial rapist, who also killed two of his victims. Prawut said the money for the bounty came from people who want to help the police nail down this repeat offender.
"These are serious crimes that have come under public spotlight," deputy national police chief General Worapong Chewprecha said yesterday.
He was speaking after holding an hours-long meeting with several senior police officers, including the Office of Police Forensic Science acting chief Pol Lt-General Manu Mekmok and Provincial Police Region 7 commissioner Lt-General Weerapong Cheunpakdee. "We will try to track down the culprit as soon as possible," Weerapong promised.
Meanwhile, the deputy police chief quoted the most latest victim as saying that the attacker was wearing a long-sleeved, deep-blue T-shirt with the word "Prasert" printed on the left-side of the chest.
"There were some small letters under the word, so we believe the T-shirt might have been a complimentary gift to customers. If we can trace the origins of the T-shirt, we should come closer to identifying the culprit," he said.
He added that local police in target areas had been instructed to contact shops and T-shirt factories to look for relevant information.
"We are checking all the possible clues," Worapong said.
He also visited the latest victim later in the day. The woman has moved to her relative's house after being attacked in her own home.
Assistant national police chief Lt-General Sopon Pisuttiwong said a war room would be set up today to facilitate efforts to track down the culprit.
"We may not be able to specify the time frame, but we will definitely arrest him," he said.
According to Sopon, the war room will be used to monitor progress on the ongoing investigations in various aspects and facilitate relevant operations.