BANGKOK (Reuters) - Thailand has freed a political activist after eight years in jail for insulting the country's widely revered monarchy under its draconian royal defamation laws.

Daranee Charnchoengsilpakul, also known as "Da Torpedo", was freed on Saturday under an annual series of royal pardons, Charnchao Chaiyanukij, permanent secretary of the Justice Ministry, told Reuters.

She was originally sentenced to 15 years in prison, he said.

Daranee, a key supporter of ousted former prime minister Thaksin Shinawatra, was convicted of making defamatory comments against the monarchy during a fiery speech at a political rally in 2008.

The Criminal Court found her guilty on three counts of lese-majeste.

Under Article 112 of Thailand's criminal code, anyone who "defames, insults or threatens the king, queen, heir-apparent or regent" faces up to 15 years in prison.

Since seizing power in 2014, the military junta has taken a hardline stance against perceived royal insults and handed down record sentences.

For more than a decade, Thailand has been bitterly divided between rival camps, one led by Thaksin, the other dominated by the royalist and military establishment who accuse Thaksin of corruption and nepotism, charges he denies.

National anxiety over the frail health of 88-year-old King Bhumibol Adulyadej has compounded the political tensions. Thais mostly see the king as a unifying force and celebrated the 70th year of his reign in June.

(Reporting by Pracha Hariraksapitak; Writing by Orathai Sriring; Editing by Andrew R.C. Marshall and Stephen Coates)