On Tuesday the Association of South-East Asian Nations (Asean) declined a Cambodian request to help resolve the dispute after Thailand objected.
The conflict focuses on an area of land of just over 5 sq km surrounding the 11th century Khmer era Preah Vihear temple.
The 11th-century temple was built in the reign of King Suryvarman I, during the 600-year Khmer empire.
Built to honour the Hindu god Shiva, the temple has withstood decades of war.
In 1998, hundreds of Khmer Rouge guerrillas made their final surrender at the temple.
Unesco deemed the temple a World Heritage site for its location, rare architecture, religious function and carved stone ornaments.
Ownership of the temple itself was awarded to Cambodia by an international court in 1962, but the ownership of the surrounding land has remained in dispute.
The recent listing of the temple as a UN World Heritage site has revived nationalist tensions in Thailand and Cambodia.
In Thailand critics of the country's prime minister, Samak Sundaravej, say the government's backing of Cambodia's application for World Heritage status undercut Thailand's claim to land around the temple.
In Cambodia meanwhile, with elections due on July 27, the dispute has become a matter of national pride.
Al Jazeera's Marga Ortigas, reporting from Phnom Penh, said the row has stirred popular sentiment with calls growing for a boycott of Thai products and candidates from all parties seizing on the issue.
Riot police equipped with water canon have been deployed outside the Thai embassy in the Cambodian capital in case rising nationalist fervour leads to violence.
The two sides have between them deployed about 4,000 troops in the area surrounding the Preah Vihear temple.
Both countries have said they will not resort to force, but with nerves on edge diplomats fear that even the smallest misunderstanding could spark a deadly exchange.
On Monday talks between Thai and Cambodian defence officials in Bangkok broke down without any agreement.