BANGKOK • Thai police have expanded their investigation to cover suspicious vehicles and online posts in a bid to trace former prime minister Yingluck Shinawatra's movements before her disappearance.

There has been no evidence so far to show she has fled or is still in the country, deputy police chief Srivara Rangsibrahmanakul told a press conference on Friday.

He said the police were particularly interested in a police pickup truck reportedly seen being driven out of the former premier's residence on Aug 23. Investigators later learnt it was a vehicle from Lat Phrao Police Station - which has jurisdiction covering the area - on a regular patrol.

However, Mr Srivara said he had ordered that the truck be checked to see whether traces of DNA, other than that of the officers, could be found and, if so, to whom they belonged.

He added that investigators were also focusing on a suspicious car that could have been involved in the former premier's escape, but he refused to give further details.

Yingluck did not show up for the Supreme Court verdict reading on Aug 25 in a dereliction case against her over her government's rice pledging scheme.

There has been much public speculation about the police vehicle since Isra News Agency released a video clip of the pickup being driven out of Yingluck's residence on Aug 23.

The Central Investigation Bureau has been instructed to check Yingluck's Facebook posts in the days before she disappeared.

Mr Srivara said the police had found another vehicle they suspected could have been involved in Yingluck's disappearance. They said it did not appear in the released video clip, but he declined to give further details.

The police have also received responses from Interpol officers in Cambodia, Singapore and Dubai, who confirmed they had no evidence of Yingluck entering these countries.

The Thai border police have also not found any trace of her slipping through Thai borders, Mr Srivara said, but added that it was possible for her to have slipped through unnoticed.

Meanwhile, army commander- in-chief Chalermchai Sitthisart conceded on Friday that there has been no progress in finding any evidence in Thailand's border areas that might be relevant to the investigation.

The army chief, in his capacity as secretary of the National Council for Peace and Order, said the junta has not abandoned its hope of finding Yingluck, and he was not worried that the ongoing inquiry would cause unrest.

On Friday, Yingluck's niece, the youngest daughter of former Thai prime minister Thaksin Shinawatra, posted on Facebook and Instagram, saying the unfortunate events experienced by her family showed that they are loved and not forgotten by the people.

"I would like to thank unfortunate events that let us know how lucky we are to have a family whose members love one another and to have friends who are ready to stand by us, as well as to have the people who have never forgotten us," Ms Paetongtan wrote in Thai.

"And the people understand that (my) father and aunt love the people and the country more than anything else."

Thaksin was ousted in a 2006 coup and lives in self-exile to avoid a 2008 graft conviction, which he said was politically motivated.

THE NATION/ASIA NEWS NETWORK