Police said at least two people Wednesday fired on the home of Kwanchai Praipana, a leader of the United Front for Democracy Against Dictatorship, a grass-roots group known for wearing red shirts that helped Yingluck get elected in 2011, the Wall Street Journal reported.
Kwanchai was shot in the shoulder and thigh, police said.
Demonstrators marched to Bangkok police headquarters to protest imposition of the state of emergency for the capital city and surrounding provinces so police can address the massive protests.
Protesters also demonstrated at a Defense Ministry facility north of Bangkok. The demonstration prompted Yingluck and other ministers attending a security meeting at the facility to leave for an unknown location, the Journal said.
Protest leader Suthep Thaugsuban said his supporters will defy the order and that the rallies will go on, the Bangkok Post reported Wednesday.
"Is there anything that is an emergency in this country? We have been protesting for three months already. Why declare an emergency now?" said Suthep, leader of the protest movement People's Democratic Reform Committee.
"We will defy them all," he said. "We will march on every road they have banned [us from marching on]. We will use loudspeakers even if they prohibit us from doing so. We will do everything they forbid us to do."
The government is expected to announce the measures it will use under the decree Wednesday. The decree will remain in effect for 60 days.
Pavin Chachavalpongpun, a professor at the Center for Southeast Asia Studies at Kyoto University, told the Journal he didn't think the emergency declaration would change much in Thailand.
"I do not believe the decree will be able to disperse the protest," he said. "If anything it could encourage the protesters to incite more violence to challenge the decree."
Bombings that killed one person and injured dozens in recent days have fueled concerns that the violence could escalate in the run-up to the Feb. 2 elections that Yingluck and her allies are expected to win. Opposition leaders said they would sit out the balloting.
The protesters oppose the election being overseen by Yingluck's government, demanding that it be conducted by a "people's council." They maintain her government is corrupt and controlled by her brother Thaksin -- a former prime minister and a telecommunications billionaire living in exile since his ouster in a 2006 coup. The government denies the allegations.
Thailand's Election Commission asked the country's Constitutional Court Wednesday to rule on whether it or the government can delay the election. The Journal said it wasn't clear whether the court will accept the commission's petition.
In a statement Tuesday, U.S. State Department spokeswoman Marie Harf said the United States "strongly condemns increasing violence in Bangkok that has resulted in deaths and injuries." The statement urged Thai authorities to investigate the attacks and bring those responsible to justice.
"The United States supports democratic institutions and processes in Thailand, our long-time friend and ally," she said. "We encourage all involved to commit to sincere dialogue to resolve political differences peacefully and democratically.
Thailand's military earlier blocked attempts to impose the emergency decree but relented after a wave of attacks on the protesters as their Bangkok shutdown operation entered a second week, the Post said.
A military source told the Post the army understands the police force needs a tool to help enforce the decree, under which a suspect can be held for up to 30 days. However, the source was quoted as saying the military will not crack down on or confront protesters.