BANGKOK - LEADERS of a long-running protest in Thailand surrendered to police on Friday on charges of inciting unrest, but are expected to win bail immediately and continue their five-month campaign to unseat the government.

The Court of Appeals quashed treason charges against the People's Alliance for Democracy (PAD) leaders on Thursday and freed two already in custody on bail for the lesser offence of inciting unrest, which still carries up to seven years in jail.

The original arrest orders for treason were issued on Aug 27, the day after PAD protesters armed with golf clubs, stakes and machetes stormed a state television station, broke into ministries and over-ran the prime minister's official compound.

Several police officers were shot, one was skewered with a flag pole and another was run over by a truck.

The unrest has hit investor confidence and distracted policymakers from focusing on slowing economic growth and the fallout from the global credit crisis, analysts say. Consumer confidence hit a 10-month low in September.

Police have denied PAD claims that they fired explosives into the crowd this week, insisting they only used teargas.

Several doctors at Chulalongkorn University, Bangkok's top medical school, have launched a campaign to deny medical services to police or politicians involved in Tuesday's clashes, the worst street violence in Thailand in 16 years.

Queen Sirikit has donated 1 million baht (S$43,310) to help treat the injured, including the police, and sent a wreath to the funeral of a 28-year-old woman killed in Tuesday's running battles with police.

The PAD leaders trumpeted the latter action as explicit support for their cause from the palace, which wields enormous moral clout in a country where the king is held in semi-divine regard.

Thailand's political crisis dates back to late 2005, when the PAD first started its street protests against then Prime Minister Thaksin Shinawatra. It has meandered through a military coup to elections and back to street protests.

It is not clear how it will end, although pressure is mounting on army chief Anupong Paochinda to launch another military coup, even though he has stressed repeatedly that it would do nothing to defuse the underlying political tensions.

In a front page interview with the Bangkok Post on Friday, ex-premier and former army chief Chavalit Yongchaiyudh, who resigned from the cabinet on Tuesday to take responsibility for the police action, said a coup was the only solution.

'After the military steps in, power should immediately be returned to the people and an interim government can be formed in which every party takes part,' he was quoted as saying.