Thailand announced on Monday it was suspending the implementation of a peace agreement with Cambodia after a landmine blast injured two Thai soldiers near the border.

The deal, overseen by US President Donald Trump, was meant to secure a lasting end to hostilities following border clashes in July that killed at least 43 people and displaced more than 300,000 civilians on both sides.

The Royal Thai Army said in a statement that the mine explosion in Sisaket Province left one soldier with a severe leg injury, while pressure from the blast caused chest pains in another.

Thai government spokesman Siripong Angkasakulkiat said Bangkok would cease "the follow-up to the joint declaration", meaning the accord with Cambodia inked in Kuala Lumpur in late October, months after the two sides had agreed a ceasefire.

The next steps planned as part of the agreement's implementation included the release of 18 Cambodian soldiers detained in Thailand.

Thai Prime Minister Anutin Charnvirakul said "we thought that the security threat had eased, but it has not actually decreased".

Cambodian authorities did not immediately comment on the incident, but have in the past denied Thai accusations of planting new landmines along the border.

Cambodia's defence ministry pledged in a statement on Monday an "unwavering commitment" to peace.

The Southeast Asian neighbours have a dispute over parts of their border dating back more than a century, but July's fighting was sparked by Thailand's claims that Cambodia planted landmines that wounded its troops.

Thailand and Cambodia agreed an initial truce in late July after intervention by Trump, as well as Chinese diplomats and Malaysian Prime Minister Anwar Ibrahim, who chairs Asean.

The new joint declaration signed in October said the two sides would organise mine clearing efforts along their border, withdraw heavy weapons and allow access to ceasefire monitor teams organised by the Asean bloc.

Thailand promised to release 18 Cambodian soldiers it has held in captivity for the past few months.

Following the signing, Cambodia's defence ministry said it was withdrawing heavy and destructive weapons from its border with Thailand.

The Thai-Cambodia truce has generally held since July 29.

But the countries have traded allegations of ceasefire breaches, and analysts say a comprehensive peace pact adjudicating the territorial dispute at the core of the conflict remains elusive. (AFP)