The People's Democratic Reform Committee spokesman, Akanat Promphan says demonstrations will continue until Prime Minister Yingluck Shinawatra steps down.

BANGKOK—The first day of a state of emergency began here Wednesday with raucous street protests and more questions about whether Thailand's army would step in to take control as civil unrest continues to trouble the country.

So far, the armed forces have kept out of the struggle between the elected government of Prime Minister Yingluck Shinawatra and royalist protesters aiming to check the power of populist leaders. But Thailand's army chief, Gen. Prayuth Chan-ocha said Wednesday: "If the situation escalates to a level where it cannot be resolved, the military will have no choice but to solve it." The 59-year-old general was speaking to reporters during a visit to Thailand's southern provinces.

Kwanchai Praipana is wheeled into an intensive-care room after he was shot and wounded outside his house in Udon Thani. nir elias/Reuters

Key Players

Read more about some key Thai political figures.

Photos: Protests Escalate

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Timeline: Legacy of Turmoil

A decade and a half after Thaksin Shinawatra founded his 'Thais Love Thais' party, antagonism prevails.

The military has completed or attempted 18 coups since the end of Thailand's absolute monarchy more than 80 years ago.

The emergency security laws that took effect Wednesday appear to have done little to quell the protests, which aim to force the government to step down in favor of an unelected, vaguely defined council. The emergency laws provide for curfews, warrantless arrests and media censorship.

In Bangkok, demonstrators marched on Royal Thai Police headquarters where they ripped signs off the walls and sprayed graffiti in a sign of defiance. "We will keep marching until we have our victory," yelled one of the leaders, Nitithorn Lamlua.

Elsewhere in the city, protesters marched to a defense ministry building where Ms. Yingluck was meeting with her security team, forcing her to leave the facility for another, unknown location.

In northeast Thailand, where support for Ms. Yingluck remains strong and the security laws don't apply, unidentified gunmen shot and wounded the leader of an influential pro-government faction, the Red Shirts. Police said the activist, Kwanchai Praipana, was shot in the shoulder and thigh.

Like other top Thai military commanders before him, Gen. Prayuth makes frequent displays of obedience to Thailand's 86-year-old monarch King Bhumibol Adulyadej and Queen Sirikit, 81, whom he refers to as "my queen," according to people who know him. Over the decades, the army has derived much of its political power from its close association with the monarchy rather than the government.

Thai antigovernment protesters wave national flags outside the governor's office in Pattani, southern Thailand, on Wednesday. Agence France-Presse/Getty Images

The outcome of the current power struggle may depend on whether the armed forces can withstand pressure to step in. The longer the impasse drags on, the greater the risk of clashes between pro- and antigovernment factions. "All this places an extreme burden on Gen. Prayuth to intervene," says Paul Chambers, a professor at Chiang Mai University in northern Thailand.

The shooting of Mr. Kwanchai was the latest violent attack associated with Thailand's political conflicts, which have been the ostensible reason for invoking the state of emergency. Since Friday, one person has been killed and dozens have been injured in grenade attacks on protest marches in Bangkok. In all, nine people have been killed since the protests began in November.

Political commentators say the frequency of attacks could accelerate ahead of elections planned for Feb. 2. Ms. Yingluck hopes the vote will restore some calm to the country. But protesters led by former deputy prime minister Suthep Thaugsuban say they aim to derail the elections, by force if necessary.

"We are looking at a very volatile situation from now until the election. I predict more deaths and casualties, despite the emergency decree being put in place," said Pavin Chachavalpongpun, a professor at the Center for Southeast Asian Studies at Kyoto University.

Write to James Hookway at