Abhisit Vejjajiva, the former Thai prime minister, has been charged with murder over the death of a taxi driver shot by soldiers during political violence.
Abhisit Vejjajiva was prime minister when thousands of protesters took to the streets in 2010 demanding his government step down.
He gave orders allowing troops to use live ammunition on protesters, who had shut down parts of Bangkok.
Abhisit Vejjajiva denies the charge, which supporters say is politically motivated.
More than 90 people, both civilians and soldiers, were killed in the protests, which went on for over two months.
Abhisit Vejjajiva and his deputy at the time, Suthep Thaugsuban, are the first officials to face charges in connection with the deaths.
The move was announced last week, after a court ruled in September that taxi driver Phan Kamkong had been killed by troops.
Now the leader of the opposition, Abhisit Vejjajiva has defended his order for live ammunition to be used, saying government forces had “very little option” but to act when live fire was used against them.
“We tried to negotiate with the protesters, and they wouldn’t accept any of the deals that we offered them,” he said.
“It was our duty to restore order, and that’s what we were trying to do.”
Abhisit Vejjajiva said he would fight to prove he was not guilty.
Elections held after the protests, in July 2011, were won by the party led by Yingluck Shinawatra, sister of Thaksin Shinawatra, the ousted prime minister whom many of the protesters backed.
Twenty-four protest leaders are also being prosecuted on terrorism charges.