Yingluck was thrown out of office on Wednesday by the Constitutional Court for abuse of power, the latest twist in a nearly decade-long struggle for power between Thailand's royalist establishment and Yingluck's brother, former Prime Minister Thaksin Shinawatra.
The National Anti-Corruption Commission (NACC) was meeting on Thursday to consider a separate case of negligence against Yingluck over a rice subsidy scheme that incurred billions of dollars in losses.
"Today, the NACC will decide whether former premier Yingluck is guilty or not in the rice case and how to proceed with the case," said an official at the NACC, who declined to be identified as she was not authorised to speak to the media.
Yingluck's removal came after six months of sometimes deadly protests in the capital, Bangkok, aimed at toppling her government and ending elder brother Thaksin's influence.
Thaksin, a former telecoms tycoon who has won the unswerving loyalty of legions of Thailand's rural and urban poor, lives in exile to avoid a 2008 jail sentence for abuse of power, but he looms over politics.
The Constitutional Court, which removed two previous pro-Thaksin prime ministers in 2008, ruled that Yingluck and nine of her cabinet ministers had abused their power in 2011 over the transfer of a security agency chief.
However, the court left the Shinawatras' ruling party in charge of a caretaker administration intent on organising a July 20 general election, which Yingluck and the party would be likely to win.
Yingluck said on Wednesday she had yet to decide on her future, but a return to power via the ballot box could be blocked if the NACC case also goes against her.
Had Yingluck been prime minister, the commission could have forwarded the case to the upper house Senate to consider impeachment and a political ban, the official said. Now it might recommend criminal proceedings which could also result in a ban.
"NO POWER VACUUM"
Activists from both the pro- and anti-government sides are planning big rallies in Bangkok over coming days, raising fears of clashes. Twenty-five people have been killed and hundreds wounded since the protests began in November.
"This is the first time both sides will protest near each other and each have hardcore elements, which is extremely worrying," said political analyst Kan Yuenyong at the Siam Intelligence Unit think tank.
Grenade attacks and sporadic gun battles have become increasingly frequent as the crisis has dragged on. There were four grenade or small bomb blasts in Bangkok on Wednesday night, including one at the home of a Constitutional Court judge. No injuries were reported, police said.
The military, which has a long history of intervening in politics, has said it will try to stay out this time but would step in if violence worsened. Army spokesman Winthai Suvaree said there were no plans to increase troop numbers in Bangkok.
One undercurrent of the crisis is a deep anxiety over the issue of royal succession, with King Bhumibol Adulyadej, the world's longest-reigning monarch, 86 years old and ailing.
Crown Prince Vajiralongkorn does not command the same devotion as his father.
Pro-government "red shirt" supporters accuse the royalist establishment of "conspiring to overthrow elected governments" at a time when the traditional order in Thailand is waning.
"I would like to send a message ... from the red shirt people of the land to the elite that the person ... we are fighting is Prem Tinsulanonda," red shirt leader Jatuporn Prompan said in a televised statement on Thursday.
Prem, a retired general and head of the king's Privy Council, an appointed body that advises the monarch, is accused by many Thaksin loyalists of masterminding the 2006 coup that overthrew Thaksin and unleashed the current chaos.
More turmoil would make matters worse for Southeast Asia's second-largest economy, already teetering on the brink of recession amid weak exports, a year-long slump in industrial output and a drop in tourism, presided over by a caretaker government with curtailed powers.
Consumer confidence fell to its lowest level in more than 12 years in April as the crisis took its toll.
The caretaker cabinet appointed Commerce Minister Niwatthamrong Boonsongphaisan, who was also a deputy prime minister and is a staunch Thaksin loyalist, as interim prime minister.
"This government has been weakened for sure, but most of the cabinet has survived and there's no power vacuum," Education Minister Chaturon Chaisang told Reuters late on Wednesday.
"We will use all our power as a caretaker government to make sure a new election is scheduled."
Yingluck dissolved parliament in December and called a snap election to try to defuse the protests, but the main opposition party boycotted the vote and anti-government activists disrupted it so much it was declared void.
Yingluck and the Election Commission agreed last week a new ballot should be held on July 20, but the date has not been formally approved and it is bound to be opposed by the anti-government protesters.
Thaksin or his loyalists have won every election since 2001.
The anti-government protesters say Thaksin buys elections and, to end his hold over politics, they say reform of the electoral system has to be implemented before new polls.