A Thai court has approved an arrest warrant for ousted leader Thaksin Shinawatra on terrorism charges related to recent anti-government protests.
The nine-week protest paralysed parts of Bangkok and left more than 80 people dead.
Many of the protesters were supporters of Mr Thaksin, and the Thai government accuses him of fomenting the unrest.
In a separate development, authorities have extended an overnight curfew in Bangkok and 23 provinces.
A curfew has been in force since the government operation to disperse protesters on 19 May and the subsequent fires and unrest across the city.
Authorities said the curfew would run for four more nights, between the hours of 0000 and 0400.
Mr Thaksin was ousted by the military in a 2006 coup, then convicted of corruption in absentia. He now lives overseas.
Many of the red-shirt protesters who arrived in Bangkok on 14 March and shut down key parts of the city for two months support him.
Thai prosecutors have accused him of co-ordinating the protests, and an official said that the court found there was reason to issue a warrant.
"The court said there was enough evidence to believe that Thaksin was the mastermind, having played a significant role in instructing and manipulating the incidents," Department of Special Investigations chief Tharit Pengdit told Reuters news agency.
Mr Thaksin rejected the charges in a statement issued through a legal advisor.
"I have never supported violence," he said. "The arrest warrant against me is unfair. I am ready to prove that I am not a terrorist and the accusation is politically motivated."
This is a much more serious charge than anything Mr Thaksin has ever faced before but, say correspondents, whether the warrant will be effective is the big question.
It is not known where Mr Thaksin lives. He travels widely, splitting his time between Dubai and Montenegro, which recently issued him with a passport.