BANGKOK - A highly-placed source in the Pheu Thai party of Yingluck Shinawatra told US broadcaster CNN that the former Thai prime minister has fled to Dubai.

Yingluck left Thailand on Wednesday - two days before a verdict was due to be delivered in a trial over rice subsidies - and is now "safe and sound" in Dubai, the source said.

She was due to appear in court on Friday (Aug 25) but a warrant was issued for her arrest after she failed to show up.

Yingluck's brother Thaksin, who is also a former Thai Prime Minister, lives in Dubai and London in self-imposed exile to avoid corruption charges.

Senior police official Sriwara Rangsibhramakul told CNN that there was no official record of Yingluck leaving the country, which would suggest she slipped into a neighbouring country first by crossing over a land border.

Asked if it was possible she fled via a natural land border, Rangsibhramakul would only say: "That is possible."

At the hearing on Friday, Yingluck's lawyer said she was ill, but did not produce a medical certificate. The explanation was rejected and Thailand's Supreme Court issued an arrest warrant.

Yingluck - ousted by a military coup in 2014 - had been barred from leaving Thailand without court approval since 2015, when her trial started.

Her bail of 30 million baht (S$1.2 million), posted when the trial began more than two years ago, has been confiscated.

Yingluck faced up to 10 years in prison for alleged negligence over the rice-buying scheme, which cost the country billions of dollars.

The court has set a new date for the verdict of Sept 27.