A yellow-shirt group will rally later this month to pressure the government to reject any negative ruling by the international court against Thailand on sovereignty of land around Preah Vihear Temple.
Chaiwat Sinsuwong said the Thai Patriots would hold a mass demonstration on January 21, but the group had yet to select a venue.
Chaiwat claimed his group had gathered 570,000 signatures from Thais to reject an anticipated ruling by the International Court of Justice (ICJ) on sovereignty of the disputed area around the temple.
The group expected to gather up to 1 million signatures by January 21. These would be submitted to the Supreme Court president and military leaders to pressure the government to reject the authority of the ICJ over Thailand, he said.
The Patriots Group would also file a lawsuit against the Foreign Ministry at the Criminal Court on January 14, accusing the ministry of disseminating false information by saying Thailand could lose the legal battle over ownership of the 4.6-square kilometre plot around the ancient Hindu temple.
Foreign Minister Surapong Towichukchaikul cautioned on Saturday that Thais should also be ready for possible disappointment in the court dispute.
Cambodia has asked the ICJ for an interpretation of the scope and meaning of its 1962 verdict that the ancient Hindu temple was located on Cambodian territory.
ML Walwipha Jaroonroj said the yellow-shirt group would use the petition to pressure the government not to give the 4.6-km plot to Cambodia. She said if Thailand accepted the 1:200,000 ratio map of France, the ICJ would definitely rule in favour of Cambodia.
Democrat MP Ong-art Klampaibul said the Pheu Thai government should have a clear-cut stand in the legal battle. Ong-art said the government should not blame the previous administration for the case because the current government had a duty to fight the court battle to its full extent.