Cartoonist Somchai "Chai Ratchawat" Katanyutanan will be asked to present himself at Metropolitan Police headquarters for questioning June 5, a report by The Bangkok Post said.
Somchai works for the Thai-language national daily broadsheet newspaper Thai Rath, widely known for its sensationalist coverage of crime and accident news.
Norawich Lalang, Yingluck's lawyer, lodged police complaints accusing Somchai of defaming a public official, defaming a public official performing official duties and violating the Computer Crimes Act of 2007.
Somchai allegedly posted on his Facebook page a photograph of Yingluck delivering a speech in Mongolia with a caption that the lawsuit claims was derogatory, the Post reported.
Details of the wording weren't published by The Post.
However, an online report by The Nation newspaper published May 3 said Yingluck is suing Somchai.
The Nation reported that Somchai posted photos of Yingluck in Mongolia and at a Thai parliamentary meeting and allegedly posted the message: "Please understand that prostitutes are not bad women. Prostitutes only sell their bodies but a bad woman has been wandering around trying to sell the country."
Police investigators concluded there is a prima facie case against the cartoonist, Metropolitan Police Bureau Deputy Chief Anuchai Lekbamrung said.
Earlier this month, around 100 Red Shirt protesters gather outside the offices of Thai Rath to protest against Somchai's Facebook comments about Yingluck.
Red Shirts are members of the political pressure group United Front for Democracy Against Dictatorship. The UDD was formed in 2006 to oppose the military coup that year which overthrew Prime Minister Thaksin Shinawatra -- the current prime minister's brother -- who later went into self-exile to avoid a jail sentence for alleged corruption.
UDD allies itself with the Pheu Thai Party, formed by Thaksin in 2008 and now led by Yingluck.
Thai Rath is no stranger to controversy, having published a photograph allegedly of the body of U.S. actor David Carradine, 72, who died in a Bangkok hotel room in June 2009.
Earlier this month, hackers invaded Yingluck's website and posted a derogatory message.
The message also commented about the prime minister's intelligence and sexual practices, The Bangkok Post reported at the time. It was signed "Unlimited Hack," although the well-known group has denied perpetrating this particular effort.
The words attributed to Yingluck were in smaller letters, "I know that I am the worst prime minister ever in Thailand history!!!"
The website was quickly taken down when the hacking was discovered.
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