By Jason Szep and Martin Petty
BANGKOK (Reuters) - Thai anti-government protesters vowed to go ahead with a mass street rally on Friday in defiance of an emergency decree imposed in the capital to quell nearly a month of demonstrations demanding new elections.
A day after Prime Minister Abhisit Vejjajiva imposed a state of emergency, authorities blocked websites and shut down an influential opposition television station, sparking a scuffle between riot police and "red shirt" protesters.
Thailand's hot stock market posted its biggest drop in nearly six months. Abhisit called off a one-day trip to Vietnam for a Southeast Asian summit. Tens of thousands of protesters ignored orders to end a six-day siege of Bangkok's main shopping area.
"We will tear up all laws," Nattawut Saikua, a red shirt leader, told cheering supporters after calling for a march on Friday to 10 undisclosed points across Bangkok.
"We don't want to call it the final day, but if we can score a knockout, we definitely will," he said. "This is all for Abhisit to dissolve parliament."
Nearly 1,000 of the supporters of ousted former Prime Minister Thaksin Shinawatra tried to push through anti-riot forces guarding Thaicom Pcl's satellite earth station in northern Pathum Thani Province before retreating by evening.
The company, once owned by Thaksin, had broadcast red shirt programs before authorities took those off air on Thursday.
As authorities issued arrest warrants for 10 red shirt leaders, the risk of confrontation drove Thailand's stock index down 3.5 percent to its lowest since October 15.
"We have to admit that the political factor has affected consumers and business," Bank of Thailand Chief Economist Suchart Sakkankosone told reporters, adding unrest could influence the timing of an interest-rate rise most economists expect in June.
Foreigners, who had snapped up $1.8 billion in Thai stocks since February 22, turned net sellers for the first time in more than six weeks after a buying spree spurred by cheap valuations and Thailand's fast-recovering economy.
The Thai economy, Southeast Asia's second biggest, may lose 0.2-1.5 percentage points in growth, depending on the severity of the unrest, Kasikorn Research Center said in a research note.
Abhisit faces a difficult choice: compromise and call an election he could easily lose, or launch a crackdown on tens of thousands of protesters that could stir up even more trouble.
Most analysts doubt the authorities will use force to remove the mostly rural and working class protesters camped in Bangkok's upmarket shopping district since last Saturday - a politically risky decision for Abhisit as his 16-month-old coalition government struggles to build support outside Bangkok.
The protesters and onlookers swelled in number as the sun set and the tropical heat eased. Streets were jammed with trucks, taxis, motorbikes, food stalls, few police and mostly excited people gathered around about a dozen screens far from the center stage.
Some waved flags, lifted by rousing speeches attacking Abhisit and the emergency degree as unlawful. The crowd went wild when red shirt leader Jatuporn Prompan screamed: "We will bring back democracy... Democracy! Democracy! Democracy!"
Bangkok generally was calm but there were scattered reports of violence.
Overnight, two men on a motorbike fired into offices of the nationalist monarchist "yellow shirts," arch rivals of Thaksin and his allies, wounding two security guards. A grenade lobbed at a yellow shirt radio station failed to explode.
In 2008, the yellow shirts occupied the prime minister's office for three months and blockaded Bangkok's main airport until a court expelled the Thaksin-allied government.
Pressure is growing on Abhisit from residents in Bangkok, a stronghold of his Democrat Party, to take decisive action to end the rolling protests, which began on March 14 when up to 150,000 massed in the city's old quarter.
"Abhisit has been accused of finding it difficult to make decisions and he seems to be struggling here somewhat. But it is a difficult position. There's human cost involved," said Danny Richards, senior Asia editor at the Economist Intelligence Unit.
The emergency decree allows authorities to suspend certain civil liberties, ban public gatherings of more than five people and stop media reporting news that "causes panic."
Abhisit assured the public on Wednesday that the emergency would not be used to impose a crackdown. Recently he has offered some concessions, including dissolving parliament in December, a year early, but protesters are demanding immediate elections.
By Thursday, authorities had blocked most websites associated with the protesters and taken several opposition TV channels off air. Military checkpoints had gone up outside Bangkok to stop more from entering the sprawling city of 15 million.
"We will go on the offensive," a protest leader, Weng Tojirakarn, told Reuters. Another red shirt leader, Nattawut Saikua, said they "would not give up."
The protesters see the urbane, British-born, Oxford-educated Abhisit as a front man for an unelected elite and military intervening in politics with impunity.
(Additional reporting by Vithoon Amorn and Pracha Hariraksapitak; Editing by Nick Macfie and Ron Popeski)