"I do believe that both the Thai and Cambodian governments will adhere to peaceful ways to resolve our border conflicts.
"My intention of using peaceful approaches to settle the border dispute does not mean that the government is afraid of a war with Cambodia.
"It is also does not mean that the government is the underdog in dealings with our neighbor, as claimed by the yellow-shirt people group.
The use of force will be the last option and will be resorted to only when there is no other solution left," Mr Abhisit said.
He stressed that the government is in contact with Cambodia about removing its flag from the disputed area.
On the three demands by the yellow-shirt People’s Alliance for Democracy (PAD), Mr Abhisit said the demands would only lead to more damage to the country, instead of any benefit.
“If the government decided to withdraw from Unesco's World Heritage Committee today, there would be no Thai representatives to oppose Cambodia’s plan to also list the area near Preah Vihear temple as a world heritage site.
“Would the yellow-shirts accept responsibility for the foreseeable consequences? My decision on the issue is for the benefit of the country, not for self interest,” Mr Abhisit said.
Defence Minister Prawit Wongsuwon said fresh deployment of Cambodian troops and armour along border areas adjoining Si Sa Ket province are not cause for worry.
Gen Prawit said Cambodian troops might be on routine defence exercises. Thai solders are also on full alert, ready to protect the country's sovereignty.
Troops of both countries were doing their duty on both sides of the border, and there should not be any problem, he said.
"I believe there are no serious problems on the Thai-Cambodian border.
"The Foreign Ministry should be able settle the dispute through talks.
"Thailand and Cambodia are not involved in a serious conflict that could trigger a war,'' Gen Prawit said.
He said the flag the Cambodians put up at the entrance to the old Kaew Sikha Khiri Sawara temple in the disputed 4.6-square-kilometre area near Preah Vihear temple was actually a temple flag, and it was only a small flag.
Gen Prawit denied suggestions that Cambodian had was taking an aggressive stance towards Thailand.
Cambodian authorities had showed they were willing to cooperate by removing the insulting stone tablet in front of Wat Kaew Sikha Khiri Sawara, he said.
Deputy Prime Minister in charge of security affairs Suthep Thaugsuban said the government will not accede to the PAD's three demands, as their demands would be very difficult to carry out.
Mr Suthep called on the PAD protesters not to block roads, as they are breaking the law and inconveniencing other people.
Bangkok police will continue to negotiate with the PAD leaders and the government is willing to talk with them at any time, he added.
PAD spokesman Panthep Puapongpan said yellow-shirt activists went to the Criminal Court on Monday morning and filed a suit against four cabinet ministers, accusing them of causing Thailand a loss of sovereignty.
Mr Panthep said the lawsuit filed by Samdin Lertbutr and Tainae Mungmajon, representatives of the PAD, accused the prime minister, his deputy Suthep, Gen Prawit and Foreign Minister Kasit Piromya of violating Articles 119 and 120 of the Criminal Code, for which the maximum penalty is capital punishment.
The spokesman said the four cabinet ministers were responsible for protecting Thailand's sovereignty, but the country had lost some sovereignty to Cambodia.
Mr Samdin and Mr Tainae are two of the seven Thais arrested for illegally entering Cambodia on Dec 29 last year. They were subsequently sentenced to nine months in jail and then released and allowed to return to Thailand.
The PAD started protesting outside Government House last Tuesday, pressing the government to revoke the memorandum of understanding on boundary demarcation signed in 2000, withdraw from Unesco's World Heritage Committee and expel Cambodian people from the disputed areas.