Former Thai PM Yingluck Shinawatra has fled abroad, sources say, ahead of a verdict in her trial over a rice subsidy scheme.
Sources in her party say she made the decision to leave unexpectedly, shortly before she was due to appear at the Supreme Court on negligence charges.
Her lawyers told the court she had been unable to attend because she was ill.
But when she failed to appear, the court issued an arrest warrant for her and confiscated her bail.
Judges also postponed the verdict until 27 September.
Ms Yingluck has denied any wrongdoing in the scheme which cost Thailand billions of dollars. If found guilty at the end of her two-year trial, she could be jailed for up to 10 years and permanently banned from politics.
Sources within Ms Yingluck's Puea Thai Party told Reuters that she had "definitely left Thailand" but did not give details of her whereabouts.
Prime Minister Prayuth Chan-ocha, who heads Thailand's military government, said all routes out of the country were being closely monitored.
"I just learned that she did not show up [at court]," he told reporters. "I have ordered border checkpoints to be stepped up."
Deputy PM Prawit Wongsuwan initially said he had no information on Ms Yingluck's whereabouts but as he left a meeting in Bangkok he said: "It is possible that she has fled already."
How could Yingluck Shinawatra have left?
Analysis by Jonathan Head, BBC News, Bangkok
Yingluck Shinawatra was the most high-profile criminal defendant in Thailand and was constantly monitored by the military authorities. So how was she able to leave the country just hours before the verdict was due to be read out? Immigration authorities say they have no record of her leaving the country.
However, it is a poorly-concealed secret that some in the military government would have been happy to see her leave the country before the verdict.
Had she been convicted and jailed, she could have been seen as a victim by her supporters. The government was nervous about their reaction. Acquitting her, though, would have been equally unacceptable to her hard-line opponents, many of them very influential.
That would also have undermined the justification for the military coup which overthrew her government. So it is unlikely anyone tried to stop her leaving, or that they will try to get her back.
She could have gone to the VIP area of one of Bangkok's airports and taken a private jet out of the country or she might have driven across the border into Cambodia or Laos.
However she is most likely to have joined her brother, former prime minister Thaksin Shinawatra, who has been living mainly in Dubai since he went into exile, fleeing a Supreme Court verdict, in 2008.
What happened in court?
Ms Yingluck's lawyer had requested a delay in the ruling, telling the Supreme Court that she had vertigo and a severe headache and was unable to attend.
But the court said in a statement it did not believe she was sick as there was no medical certificate and that the claimed sickness was not severe enough to prevent her travelling to court.
"Such behaviour convincingly shows that she is a flight risk. As a result, the court has issued an arrest warrant and confiscated the posted bail money," the statement said.
Ms Yingluck posted $900,000 (£703,000) bail at the beginning of her trial.
Friday's turn of events took many by surprise, including the hundreds of people who turned up outside the Supreme Court in Bangkok to support Ms Yingluck.
BBC Thai reporter Nanchanok Wongsamuth said the announcement prompted shocked reactions in the courtroom, and then a flurry of activity as journalists ran out to report the news.
What is the trial about?
Ms Yingluck, who became Thailand's first female prime minister in 2011, was impeached in 2015 over the rice scheme by a military-backed legislature, which then brought the legal case.
The scheme, part of Ms Yingluck's election campaign platform, launched shortly after she took office.
It was aimed at boosting farmers' incomes and alleviating rural poverty, and saw the government paying farmers nearly twice the market rate for their crop.
But it hit Thailand's rice exports hard, leading to a loss of at least $8bn and huge stockpiles of rice which the government could not sell.
Though it was popular with her rural voter base, opponents said the scheme was too expensive and open to corruption.
During her trial, Ms Yingluck had argued she was not responsible for the day-to-day running of the scheme. She has insisted she is a victim of political persecution.
In another development on Friday, former Thai minister Boonsong Teriyapirom was jailed for 42 years in connection with the rice subsidy scheme.
The BBC's Jonathan Head in Bangkok says the exceptionally heavy sentence for Mr Boonsong suggests the court would not have been lenient with Ms Yingluck and it is possible she was warned about this before making her decision to flee.
How popular is Yingluck Shinawatra?
Ms Yingluck's time in office was overshadowed by controversy as well as strong political opposition.
The youngest sister of Mr Thaksin, she was seen by her opponents as a proxy for her brother, who was controversially ousted by the military in 2006.
Both siblings remain popular among the rural poor, but are hated by an urban and middle-class elite.
Their Puea Thai party has - under various different names - won every election in Thailand since 2001.
Some of Ms Yingluck's supporters outside the court on Friday expressed understanding at her failure to show.
"The Thai prime minister has done her best, she has sacrificed a lot," said Seksan Chalitaporn, 64. "Now the people have to fight for themselves."
Telecommunications billionaire Mr Thaksin, who once owned Manchester City FC, has lived in self-imposed exile since leaving Thailand. It is believed he travels between homes in London, Dubai, Hong Kong and Singapore.
Timeline of Yingluck's rice scheme controversy
May 2011- Yingluck Shinawatra is elected PM, and shortly afterwards begins rolling out her rice subsidy scheme.
January 2014 - Thailand's anti-corruption authorities investigate Ms Yingluck in connection to the scheme.
May 2014 - She is forced to step down from her post after Thailand's constitutional court finds her guilty of abuse of power in another case. Weeks later the military ousts what remains of her government.
January 2015 - An army-backed legislature impeaches Ms Yingluck for corruption over her role in the rice scheme, which effectively bans her from politics for five years. It also launches legal proceedings against her.
August 2017 - Ms Yingluck fails to appear at court for the verdict, claiming ill health.