Wason Wanichakorn, Associated Press
Thai police officers shoot tear gas into anti-government crowd besieging their headquarters Friday in Bangkok.

BANGKOK, Thailand — Thai police fired tear gas at thousands of right-wing protesters besieging their headquarters Friday, while demonstrators outside the capital disrupted air and rail service in a growing campaign to unseat the prime minister.

Saying that Western-style democracy has allowed corruption to flourish, the protesters have said they hope to repeat their success of two years ago, when they helped topple former Prime Minister Thaksin Shinawatra.

Prime Minister Samak Sundaravej insisted he won't step down, and may declare a state of emergency, suspending some civil liberties, if rioting during the four-day old protest worsens. The country's influential army commander said the military will steer clear of politics and not stage a coup.

The People's Alliance for Democracy protesters settled in for a fourth night occupying the grounds housing his offices. They have fought police — under orders to show restraint — to a standoff.

"After the current government is ousted, we will propose a totally new political system with those corrupt guys prosecuted and we will have a clean and efficient political system," protest leader Sondhi Limthongkul told The Associated Press.

The alliance accuses Samak's government of serving as a proxy for Thaksin, who was deposed in a bloodless coup and banned from public office until 2012. Thaksin, who fled to self-imposed exile in Britain, faces an array of corruption charges.

Samak led Thaksin's political allies to a December 2007 election victory, and their assumption of power triggered fears that Thaksin would make a political comeback on the strength of his continued popularity with Thailand's rural majority.

The protesting alliance and its sympathizers — monarchists, the military and the urban elite — complain that Western-style democracy of one man, one vote gives too much weight to Thailand's rural majority, whom they consider unsophisticated and susceptible to vote buying.

In such a system, they say, money politics fuels corruption and bad governance.

Friday saw the worst unrest in the latest round of protests.

After police forced their way into the Government House compound to deliver a court eviction order, the alliance fought police in running street battles, charging, punching and hitting officers with sticks. They withdrew to display minor injuries they got when police fought back.

Claiming "police brutality," alliance members later laid siege to city police headquarters, saying they wanted officers they accuse of violence surrendered to them. As they pressed against the gates, police threw tear gas canisters to disperse them.

"The situation is out of control," said police spokesman Surapol Tuantong.

Samak insisted the government would not employ force, but rather "soft and gentle" methods to oust the protesters, indicating he was willing to wait out the protesters, whose numbers go up and down from 2,000 to about 30,000.

He accused the protesters of trying to spark a confrontation with authorities that would lead to violence.

"They want bloodshed in the country. They want the military to come out and do the coup again," he said.

Thousands of protesters meanwhile blockaded passengers from entering three airports in southern Thailand, forcing their closures.

Hundreds of railway workers staged a work stoppage by taking emergency sick leave, forcing the cancellation of 76 passenger trains and 30 cargo trains throughout the country, authorities said.

In July, the protest group unveiled its blueprint for a new government, which would roll back Thailand's democratic gains of the post-1973 dictatorship era and make parliament a mostly appointed body.

The alliance suggests that 30 percent of lawmakers could be elected, and 70 percent chosen from various occupations and professions.

Similar ideas have been floated before, most notably in 1983. The general who was then serving as prime minister — Prem Tinsulanoda, now an adviser to King Bhumibol Adulyadej — found himself frustrated by having to compromise with the elected politicians in his Cabinet.

The power of the elite has steadily dissipated since the 1932 overthrow of the absolute monarchy, with the growth of the middle class forcing a sharing of the spoils. Thaksin's empowerment of the rural majority — whom he wooed with unprecedented welfare programs — threatened their privilege more.