Authorities in Thailand have accused Cambodia of violating the ceasefire the two countries agreed to on Monday, following economic pressure from the Trump administration.
The truce, which was signed in Malaysia, was supposed to come into force at midnight, bringing an end to cross-border clashes that have killed at least 41 people and displaced thousands.
The Thai army accused Cambodia of launching attacks in multiple areas early on Tuesday but Cambodia said there was no firing in any location.
Thailand later said fighting had stopped after military commanders along the border from both sides met.
They agreed to halt troop movements, avoid escalation and establish coordination teams ahead of a joint border committee meeting in Cambodia on 4 August, army spokesperson Major General Winthai Suvaree said.
Cambodian Defence Minister Tea Seiha said he spoke to his Thai counterpart about "incidents" that occurred during the implementation of the ceasefire but stressed the Cambodian army abided by the truce.
He said Cambodian defence officials will lead a delegation of diplomats, foreign military attachés and others to observe the situation.
The Thai government separately said it has lodged complaints to Malaysia, the US and China about Cambodia’s alleged breach of the ceasefire agreement.
Along the border, there were signs of calm with some of the more than 260,000 people displaced by the fighting returning to their homes.
Ceasefire struck under US pressure
Cambodian Prime Minister Hun Manet and Thailand's acting Prime Minister Phumtham Wechayachai agreed to an “unconditional” halt in fighting on Monday in talks hosted by Malaysian Prime Minister Anwar Ibrahim.
He called the ceasefire a "vital first step towards de-escalation and the restoration of peace and security."
Secretary of State Marco Rubio said the US applauded the ceasefire declaration.
"President Trump and I are committed to an immediate cessation of violence and expect the governments of Cambodia and Thailand to fully honour their commitments to end this conflict," Rubio said in a statement.
Hun Manet said on Tuesday that Trump had called to offer congratulations for the peace agreement.
He posted on social media that Trump pledged the US would join the monitoring process along with Malaysia to ensure the ceasefire is implemented.
Trump also called Phumtham after his return to Bangkok.
Phumtham said Trump told him that Thailand’s talks with Washington to negotiate tariff levels on Thai exports could now proceed and that he would seek to make them as favourable as possible.
The ceasefire comes days before the US is expected to announce new trade tariff decisions.
Cambodia and Thailand have both been two of the hardest-hit countries as a result of Trump’s trade war, with a 36% tariff on goods from both countries due to take effect on Friday.
Trump had warned that the US might not proceed with trade deals with either country if hostilities continued, giving both sides a face-saving justification for halting the clashes.
Caution among border residents
Cambodia and Thailand have clashed in the past over their 800-kilometre border.
The latest fighting began on Thursday after a landmine explosion wounded five Thai soldiers.
Tensions had been growing since May when a Cambodian soldier was killed in a confrontation that created a diplomatic rift that roiled Thailand's domestic politics.
Residents on both sides of the border expressed relief about the ceasefire but remained wary, unsure how long the peace would last.
"I am very concerned that new fighting may break out. Thailand often provokes the fighting first, but then accuses Cambodia. Their aims is that they want to occupy our temples. I really don’t want to see any new fighting happen," said Soklang Slay, as he helped his daughter move back into her home in Cambodia's Oddar Meanchay province.
Meanwhile, in Thailand's Surin province, local community leader Kritsada Jindasri said he heard heavy firing and explosions on Monday night before silence fell at midnight.
"We are still cautious. We still don't totally believe (that it would stop). We still wait to assess the situation," said Kitsada, who had stayed back along with 60 other community leaders after some 400 villagers evacuated last week.
