The International Court of Justice (ICJ) has no authority to interpret its own 1962 ruling over the disputed territory around the Preah Vihear temple, the Foreign Ministry's legal team says.
Cambodia failed to follow proper procedures in making a request for an interpretation on the issue, Darm Boontham, director of the Boundary Division under the ministry's Department of Treaties and Legal Affairs said.
Mr Darm was giving evidence before a House committee on state security about the strategy which the country's legal team will pursue in handling the dispute.
Cambodia has asked the ICJ to interpret its 1962 judgement, which awarded ownership of the Preah Vihear temple to Phnom Penh.
An area of 4.6 square kilometres surrounding the temple has remained a source of dispute and is claimed by both countries.
The earlier decision did not cover the disputed area.
Mr Darm said Cambodia is seeking the ICJ's interpretation on a new issue which was not part of the old case.
It was being asked to give judgement on the disputed area rather than the temple, which was wrong.
Cambodia's request for an interpretation is an appeal in disguise, he said, which he said was a breach of the ICJ's charter.
He said the ICJ's charter does not allow an appeal to be submitted in a case which is already final.
The court's charter, which authorises it to re-interpret previous cases and rulings, has no bearing, he said.
The Foreign Ministry's legal team will tell the court that Thailand has fully complied with its 1962 ruling, he said.
In 1962, the cabinet issued a resolution to erect a fence around the disputed area.
Cambodia has not protested about the fencing in over 50 years, Mr Darm said.
That shows that Cambodia has accepted Thailand's rights over the area.
However, Thailand will respect the ICJ's ruling in October no matter the outcome, he said.
The cabinet will have to consider how to comply with the court's ruling, he said.
Thailand and Cambodia will present their oral statements to the judges on April 15-19.