Thai prosecutors have said former prime minister Thaksin Shinawatra will be indicted for defaming the monarchy, three months after he was freed on parole on other charges.

He will not be immediately arrested after filing a postponement request on Wednesday after contracting Covid-19.

Prayuth Bejraguna, spokesperson for the Office of the Attorney General, said at a news conference that officials had verified that he was ill.

The attorney general’s office has a new appointment scheduled for Thaksin’s indictment on June 18, adding that the former Thai leader will also be indicted for violating the Computer Crime Act.

Thaksin had been in self-imposed exile since 2008, but returned to Thailand in August last year to begin serving an eight-year sentence.

He was released on parole in February from a Bangkok hospital, where he spent six months serving time for corruption-related offences.

He was moved almost immediately from prison to the hospital on grounds of ill health. About a week later, King Maha Vajiralongkorn reduced his sentence to a single year.

The former prime minister was granted parole earlier this month because of his age — he is 74 — and ill health, leaving him free for the remainder of his one-year sentence.

After the return, the attorney general’s office said it had revived an investigation into whether Thaksin had violated the law against defaming the monarch almost nine years ago, a crime punishable by up to 15 years in prison.

Thaksin was initially charged in 2016 with violating the law for remarks he made to journalists in Seoul, South Korea, a year before. Officials said the investigation could proceed only after he was presented with the charge in person in the hospital in January.

He denied the charges and submitted a statement defending himself.

Mr Prayuth said there is enough evidence for the attorney general to indict Thaksin. He said the prosecutors had prepared their statement and documents to present to the court next month.

Thaksin’s lawyer Winyat Chatmontree said he is confident he has a strong defence for his client.

“We have been working on this for several months, since we submitted the statement of defence,” he told The Associated Press.

“But whether we will win the case, it’s up to the court’s discretion based on the evidence.”

Mr Winyat also claimed that the video of Thaksin’s comments that investigators used as evidence might have been manipulated.