Thai ex-prime minister Yingluck Shinawatra missed a verdict in a negligence trial on Friday that could have seen her jailed, prompting the Supreme Court to issue an arrest warrant fearing she is a flight risk, a judge said.

"Her lawyer said she is sick and asked to delay the ruling... the court does not believe she is sick... and has decided to issue an arrest warrant," lead Judge Cheep Chulamon told the court, rescheduling the ruling date to September 27.