Thailand's anti-corruption agency is to bring charges of negligence against Prime Minister Yingluck Shinawatra on Thursday as anti-government protesters demand her ouster in a violence-pocked standoff that is slipping out of control.
Intermittent bursts of gunfire and grenade blasts have become routine at night in a conflict that has taken a heavy toll on tourism in the capital, famous for its golden temples and raunchy bars.
Guitarist Eric Clapton has pulled out of Bangkok concert on Sunday because of the deteriorating security.
About 200 Yingluck supporters, who have become more boisterous in recent days, padlocked the gates of the National Anti-Corruption Commission on Thursday, demanding all members quit and setting the scene for a possible confrontation.
But the caretaker prime minister was in the northern city of Chiang Mai, her family's home town, on Wednesday and was not expected to attend the hearing.
The charges relate to a disastrous rice subsidy scheme that paid farmers above the market price but has proved ruinous to the budget, adding to the government's woes as unpaid rural workers demand their money.
The protesters, whose disruption of a general election this month left Thailand in paralysis, want to topple Yingluck and erase the influence of her brother, ousted premier Thaksin Shinawatra, seen by many as the real power in the country.
They want to set up a "people's council" of unspecified good and worthy people to spearhead political reform before new elections are held and have blocked key intersections in Bangkok for weeks to press their case.
The protests have been marked by occasional small bomb blasts and gunfire in which 21 people have been killed and more than 700 wounded since the crisis began in November.
The crisis pits the mainly middle-class and southern anti-government demonstrators, who are backed by the royalist establishment, against the largely rural supporters of Yingluck and Thaksin in the north and northeast.
Both sides have armed activists and some pro-government leaders have called for Thailand to be divided in two, along north-south political lines, prompting talk of a possible civil war.
"As of now, there is no clear sign that (civil war) will happen," national security chief Paradorn Pattanatabutr told Reuters.
"There are those who think differently and respect the law who can no longer tolerate this ... The government must do everything it can to avoid confrontation and to prevent each side setting up stages or rallies near each other.
"If they can do that, there should be no incidents."
The standoff also raises the question of whether the military will step in, as they have many times before, most recently in 2006 to remove Thaksin, although the army chief has ruled out intervention this time.
Thaksin's enemies say he is a corrupt, crony capitalist who manipulates the masses with populist handouts and is a threat to the monarchy, which he denies.