Prime Minister Yingluck Shinawatra declared a 60-day state of emergency in Bangkok and surrounding areas from Wednesday, hoping to prevent an escalation in the protests now in their third month.
The Election Commission says the country is too volatile to hold a general election now and that technicalities mean it is anyway bound to result in a parliament with too few lawmakers to form a quorum.
The government says the decree to hold the election on that date has been signed by the king and cannot be changed.
"The Constitutional Court has accepted this case and we will look at the legal issues involved. If there is enough evidence, we may hand down a decision on Friday," said court spokesman Pimol Thampithakpong.
The protests are the latest eruption in a political conflict that has gripped the country for eight years. The emergency decree failed to clear the demonstrators, though the capital has been relatively calm this week.
Broadly, the conflict pits the Bangkok middle class and royalist establishment against the mainly poorer supporters of Yingluck and her brother, ex-premier Thaksin Shinawatra, who was toppled by the military in 2006.
Nine people have been killed in outbursts of violence, including two grenade attacks in Bangkok last weekend.
A leading pro-government activist was shot and wounded on Wednesday in Thailand's northeast, a stronghold of the Shinawatra family, in what police said may have been a political attack, adding to fears the violence could spread.
A ruling in favour of the Election Commission would deepen Thailand's political quagmire, already weighing on investor enthusiasm for Southeast Asia's second-biggest economy.
The main opposition Democrat Party says it will boycott the vote. Protest leader Suthep Thaugsuban, a former Democrat minister, wants democracy suspended so that a "people's council" can push through electoral and political changes.
Thais living overseas have already voted and some advance voting takes place around the country on Sunday. The protesters have said they would try to disrupt the election.


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