A Thai court has warned the government not to use force against protesters, a day after clashes with police left five people dead.
But the Civil Court on Wednesday refused the opposition's demand to strike down a 60-day emergency decree put in place in late January.
The government has used the emergency decree to arrest top protest leaders and disperse some opposition protest camps in Bangkok.
On Tuesday, four protesters and a police man were killed and dozens wounded in a midday clash on a major avenue in the capital.
Despite the violence, opposition protesters stepped up their campaign Wednesday, though there was no repeat of the clashes.
Thousands of anti-government protesters surrounded the prime minister's temporary office in Bangkok, as soldiers looked on from behind barbed-wire fences.
Prime Minister Yingluck stayed away from the office. A top security official said there would be no immediate moves to break up any more protests.
But protest leader Suthep Thaugsuban has vowed to keep pressure on Ms. Yingluck, whom he says was responsible for the "excessive and unnecessary" violence.
"The masses of people don't want to let Yingluck Shinawatra come and use this building, which was built by taxpayers' money, to be used as her hiding place and her office any longer."
Both sides appeared to be using weapons during the Tuesday conflict near the Government House in central Bangkok. A Human Rights Watch researcher told VOA that militants had M79 grenade launchers and were firing at police.
At least 15 people have been killed in Thailand since November, in the country's worst political violence since 2010. Ms. Yingluck's opponents contend her government is corrupt and controlled by her billionaire brother, exiled ex-prime minister Thaksin Shinawatra.
Ms. Yingluck tried to resolve the conflict with early elections this month. But the opposition boycotted the vote, and disrupted it in several areas, preventing a definitive result until more polls can be held.