A helicopter collected a Thai soldier injured in a landmine explosion along the Thai-Cambodia border - one of the events triggering the deadly attacks on Thursday.

Footage shows the aircraft arriving to airlift Sergeant Major First Class Phichitchai Boonchula to a hospital in Ubon Ratchathani on July 23.

The officer and four others were patrolling the Chong Arn Ma area when the explosive - one of six million unexploded devices left by the Americans and assisted by Thai leaders in the 1960s and 70s - reportedly blew up at around 4:55 pm on Wednesday.

All five were taken to the Namyuen Hospital, and four of them were later transferred to Fort Sunpasitthiprasong Hospital in the 22nd Military District.

Lieutenant General Boonsin Padklang, commander of the Second Army Area, said military officials responded by closing the Prasat Ta Muen Thom and Prasat Ta Krabey ancient Khmer temples, and sealing four border checkpoints.

Acting Prime Minister Phumtham Wechayachai, who also serves as Interior Minister, ordered a diplomatic downgrade following the incident.

The Thai military is also said to have attacked Khmer positions in the early hours of July 24. Cambodia claims it responded by launching rockets into Thailand, killing at least 14 civilians.

Prime Minister Phumtham said: 'The government has decided to downgrade diplomatic relations by recalling the Thai ambassador to Cambodia back to Thailand and sending the Cambodian ambassador to Thailand back to his country as well. We will consider the level of relations further.'

Just a week earlier, three Thai soldiers were injured, with one of them losing his leg, after landmines exploded during their patrol of the Chong Bok border area in Ubon Ratchathani.

Thai authorities said they will seek recourse through bilateral channels, and urged Cambodia to 'cooperate on humanitarian demining efforts along the border of the two countries as bilaterally agreed by both Prime Ministers'.

Cambodia still has up to six million unexploded devices that were dropped by the United States. It was Thailand that provided the United States with military bases throughout the 1960s and 1970s for campaigns that resulted in the widespread presence of unexploded ordnance, including mines.

Tensions between Thailand and Cambodia escalated after a clash between troops from both countries in a disputed area in Nam Yuen district, Ubon Ratchathani, on May 28, resulting in the death of a Cambodian sergeant.

Thailand expressed its intention to resolve the dispute through existing bilateral mechanisms.

However, Cambodia vowed to take the case before the International Court of Justice in The Hague.