"It will be a significant ruling on media freedom and freedom of speech," said Supinya, secretary-general of the Campaign for Popular Media Reform.

"I don't know how the ruling will turn out, but if I lose I will appeal."

The suit was filed two years ago when the family of caretaker Prime Minister Thaksin Shinawatra owned Shin Corp. The company is also seeking Bt400 million in compensation in a civil suit. This suit could go forward if the Criminal Court rules in its favour today.

Supinya was accused of libel for saying that Shin Corp had a mutually beneficial relationship with the Thaksin administration and the ruling Thai Rak Thai Party.

Since Singapore's Temasek Holdings took over Shin Corp in January, however, the company has been under mounting pressure to drop the suit, following the public furore over the controversial sale by Thaksin's family.

A Shin lawyer had offered to withdraw the suit on condition Supinya apologised for her comments, published by the Thai Post, that the company had benefited hugely from state policies.

She turned down the offer and called on the company to acknowledge the public's right to scrutinise it.