EXILED former prime minister Thaksin Shinawatra broke his silence today with a Twitter posting, days after his younger sister Yingluck fled Thailand for an undisclosed country.

Yingluck, 50, who was Thailand's first female prime minister fled the country after failing to turn up in court last Friday to hear a key verdict which could send her to jail for up to 10 years, upon conviction.

In the tweet, where he quoted a French political philosopher, Thaksin said, "Montesquieu once said, 'There is no crueler tyranny than which is perpetuated under the shield of law and in the name of justice'."

His younger sister became Thailand's prime minister in August 2011 before being ousted in a power struggle in May 2014, days before the military staged a coup, with Yingluck facing allegations of negligence in the rice pledging scheme implemented during her administration.

Thaksin himself fled the country in 2008 to escape a corruption trial.

Meanwhile, Prime Minister Gen Prayut Chan-o-cha when met at the Government House here today, was asked about Thaksin's Twitter posting.

"Let him do that. What could (I) do? It is up to you to believe him. Think by yourself," he said while pointing at his head.

Thailand's Army chief, Gen Chalermchai Sittisart had claimed that Yingluck's escape was well-hatched and planned by her brother, Thaksin.

The country's police have begun investigation into the escape, including asking for assistance and information from several countries including Cambodia, Singapore and United Arab Emirates.

Yingluck is believed to be in Dubai, where her brother maintains a house as speculated by the media.

-- BERNAMA