Thai Premier Yingluck Shinawatra on Friday said she was taking legal advice to counter a Constitutional Court ruling that scuppered her party's plans for a fully-elected senate.
The ruling Puea Thai party has slammed the court for its Wednesday verdict that found a bill to change the make-up of parliament's upper house was "unconstitutional".
"This kind of thing has never happened before, so I will ask the Council of State to study the issue," Yingluck told reporters, referring to the government's legal advisers.
She added that she did not want to see "conflict" in the country, which has been seized by periodic bouts of sometimes bloody political turbulence since her divisive brother Thaksin was deposed in a coup seven years ago.
Puea Thai, which escaped potential dissolution by the court Wednesday, has questioned the authority of the tribunal's nine judges to rule on charter amendments that have been decided in parliament.
Spokesman Pormpong Nopparit said the party was looking at a number of legal avenues to fight the verdict, including trying to impeach the five judges who ruled the party had violated its powers in the process of passing the bill.
"I understand that impeachment might be difficult, but we have to try in order to protect people power and to assert that it is the right of the people to amend the constitution," he said.
Judicial rulings have played a key role in Thailand since the 2006 coup deposed Thaksin, who now lives in self-imposed exile abroad to avoid a conviction for corruption that he claims was politically motivated.
Two pro-Thaksin premiers were forced from office in 2008 by such rulings, making way for the opposition Democrat Party, backed by the military and Bangkok's elite, to take power in a parliamentary vote.
The scuppered Puea Thai constitutional amendment to make the upper house fully elected would have returned the senate to its structure before the 2006 coup -- a situation observers say the establishment is keen to avoid as it seeks to check Thaksin's electoral might.
The political temperature is already high after a controversial amnesty plan prompted rallies in Bangkok over fears it would have allowed Thaksin's return.
The amnesty bill was rejected by a senate vote last week, but the anti-government rallies have persisted.
Pormpong said the party is also mulling filing criminal charges against the judges under Thailand's strict royal insult laws.
"The (amendment) bill had already been submitted to the king, so the Constitutional Court had no authority to deliberate the case," he told AFP.
The monarchy is a highly sensitive topic in Thailand, where 85-year-old King Bhumibol Adulyadej is revered as a demi-god by many Thais.
Critics say charges brought under Thailand's lese majeste legislation are often politically motivated.