A Thai webmaster lost her appeal Friday against a conviction for failing to remove a comment deemed critical of the monarchy from her Internet site -- a case that triggered international alarm.

The Court of Appeals in Bangkok upheld the eight-month suspended jail sentence for Chiranuch Premchaiporn, whose prosecution stoked fears of worsening Internet freedom in the politically turbulent kingdom.

Google has branded her conviction a "serious threat" to the Internet in the country, while the European Union has expressed "deep concern".

The monarchy is a highly sensitive topic in Thailand. The 85-year-old King Bhumibol Adulyadej is revered as a demi-god by many Thais and protected by harsh royal defamation laws.

Critics say charges brought under Thailand's lese majeste legislation are often politically motivated and amount to an assault on free speech.

Chiranuch was charged over 10 comments posted on the popular Prachatai news site in 2008.

The Criminal Court, handing down the original conviction in May 2012, recognised that she had not personally committed lese majeste, but found that the 20 days she had taken to remove one of the comments was in breach of the Computer Crimes Act.

Chiranuch told AFP on Friday that she was unlikely to appeal to the Supreme Court.

She voiced concern that Thailand's regulation of the Internet was not in line with international standards under which authorities serve notice to a website that a message should be removed.

"The court said that rule cannot be applied to cases related to the monarchy," she said. "This means there is less Internet freedom than in other countries."

In January, editor Somyot Prueksakasemsuk was jailed for 11 years in connection with two articles that appeared in his magazine, to the dismay of human rights defenders.

In June, the World Association of Newspapers and News Publishers warned that royal defamation laws were creating a "climate of fear" and being misused to wrongly imprison journalists.

Under the lese majeste rules, anyone convicted of insulting the Thai king, queen, heir or regent faces up to 15 years in prison on each count.

Last month a Thai woman was jailed for five years for committing lese majeste and breaking computer crime laws with comments posted on the Prachatai news site.