Some 121 individuals and social organisations signed the open letter handed to the UN chief via officials at the UN building in Bangkok.

In it, the group said Thaksin Shinawatra's government had a poor human-rights record and treated defenders of those rights badly.

Thaksin's anti-drugs campaign killed more than 2,500 people in 2003, the group said.

And harsh handling of civil unrest in the South has seen the deaths of more than 1,000 people since the beginning of 2004.

The 2005 Emergency Law used to deal with the crisis violated people's basic rights, as it gives officials more freedom to arrest and detain suspects, the group said.

Under the Thaksin regime, there have been reports of surveillance and harassment of human rights defenders, particularly those who work on issues related to violence in the South. In March 2004, prominent Muslim lawyer Somchai Neelaphaijit disappeared in Bangkok after revealing his clients - accused of violence in the South - had been tortured. Somchai was abducted, reportedly by police, and is now presumed dead.

Media freedom and protection of refugees were also problematic under the current government, the letter to Annan said.

The groups said Annan should urge the government to review its anti-drugs campaign and avoid implementing any programme that would lead to extrajudicial killings in the future. They also called for the emergency decree to be abolished and for a review of police and state methods of dealing with the crisis in the South, as well as for respect, promotion and fulfilment of major international rights agreements.