UDON THANI, Thailand -- On a scorching afternoon in northeast Thailand, about 1,000 black-clad supporters of Prime Minister Yingluck Shinawatra clenched their fists and punched imaginary opponents with forceful uppercuts. Following the directions of a trainer on a nearby stage, they fended off kicks and practiced footwork to loud speakers blaring music typically heard at a Thai kickboxing stadium.

Sweat streamed down their faces as the men and women shouted, "We will definitely win!"

The scene in Udon Thani province last week was part of a two-day training course for farmers, labourers and others in the heart of pro-government "Red Shirt" country -- Thailand's rural, poor north and northeast.

The Red Shirts have been largely quiet since anti-Yingluck protesters largely representing the urban elite and southerners shut down key intersections in Bangkok for several weeks earlier this year. But now, with growing speculation that Thailand's constitutional court and anti-graft agency may remove Yingluck from office in what critics say would be a "judicial coup," her supporters are gearing up to march on Bangkok themselves, raising the spectre of renewed violence in Thailand's decade-long political turmoil.

"We need to show our force and stand by her side," said Sa-ngob Ratmuangsri, a 64-year-old farmer at the training session called "Volunteers' Ward to Protect the Country's Democracy."

"I wouldn't be here if I was afraid to die," he said with determination.

Thailand has been convulsed by political conflict since Yingluck's brother, former Prime Minister Thaksin Shinawatra, was deposed in a 2006 coup after being accused of corruption and abuse of power.

Both sides say they reject violence, and the Red Shirts say the kickboxing practice sessions are for self-defence, not attacking people. But since late last year at least 24 people have been killed, including several children, and more than 700 wounded in drive-by shootings, gunfights, grenade attacks and other violence. The anti-government movement has employed armed guards to escort their protest marches, and gunfights have occasionally erupted.

"We know that there are militants on both sides who have been collecting weapons. The violence during the past few months testifies to this," Michael Nelson, a Southeast Asian studies lecturer at Walailak University in the southern province of Nakhon Si Thammarat. However, he said that the actions to follow "do not necessarily mean civil war" but rather "some sort of combination of protests and guerrilla warfare."

The Red Shirts -- who got their name back in 2007 to distinguish themselves from their "Yellow Shirt" opponents at the time -- see themselves as defenders of Thailand's democracy. Yingluck's ruling Pheu Thai party won in a landslide in a 2011 election that was deemed free and fair, but she faces strong opposition from a powerful minority that brings together staunch royalists, top army brass and Bangkok's middle and upper classes, as well as backers in the south.

For their part, the anti-government protesters accuse her party of subverting democracy through corruption and populist schemes that amount to vote-buying.

Suthep Thaugsuban, leader of the so-called People's Democratic Reform Committee, told his own cheering crowds in Bangkok this past weekend he would seize power in the name of "the people" if legal rulings are issued against Yingluck's government. He promised to replace the current democratically elected administration with an unelected "people's council" that would carry out reforms to root out corruption.

The Red Shirts' new leader, Jatuporn Prompan, recently appointed head of the umbrella group United Front for Democracy Against Dictatorship, or UDD, has said his movement will remain peaceful, but promised to fight back if the country's judicial institutions remove Yingluck from power.

After Thaksin's overthrow, two pro-Thaksin premiers were forced out in controversial court rulings, and analysts say Yingluck is likely to meet the same fate.

"On the day it appears without doubt that a person who becomes the prime minister is neither a member of parliament, nor is he or she elected by the people ... on that day, a long-lasting battle will commence," Jatuporn declared in a speech this past weekend.

"We have to fight openly, peacefully and nonviolently, but I can assure you that the number of our people will be several times bigger than the PDRC," he said.

The last time the Red Shirts descended on Bangkok, in 2010, they occupied a central shopping district for two months. Suthep, deputy prime minister at the time, ordered a military crackdown that left the city's skyline in flames and nearly 100 dead.

The courts and independent state agencies are widely seen as being biased against Thaksin's political machine, and a decision by the country's anti-corruption agency in coming weeks could lead to Yingluck's impeachment by the Senate if she is accused of dereliction of duty in overseeing a contentious rice subsidy program. Yingluck said recently that she had "not been treated equitably or received any justice" in the case.

Her supporters say the country's institutions are conspiring against them.

"Since we can't rely on anyone, not the military or sometimes not even the police, we have to take the matter in our own hands," said the man leading the Red Shirt training, Suporn Atthawong, known as "Rambo of the Northeast" for his blunt, confident speech.

Suporn said his recruits are not conducting weapons training. "We believe in nonviolent approach," he said. "But I can assure you that they are willing to sacrifice their lives if necessary."

Last weekend, the Red Shirts staged their first rally in Bangkok since November. And Suporn's group has recruited about 24,000 volunteers, some of whom will be selected to join the next training later this month.

Thailand's army has staged 11 coups since the end of absolute monarchy in 1932, and there are fears it could do so again.

"If the people clash and there's bloodshed then the military will have to come out," said Prinya Thaewanarumitkul, a law lecturer at Bangkok's Thammasat University.

Some grass-root Red Shirt supporters aren't too optimistic about a peaceful solution through negotiations.

"I hope all sides can compromise," said Sumit Parito, a 43-year-old butcher who participating in the training session in Udon Thani. "But if they can't, I don't see any way for us but to rise again."