The incident near the Chong An Ma border crossing prompted the government to order the closure of all crossings in northeastern Thailand, reports the Bangkok Post.
Deputy Prime Minister Phumtham Wechayachai also announced that the government was expelling the Cambodian ambassador, Hun Saroeun, while recalling the Thai envoy from Phnom Penh.
“By recalling the Thai Ambassador from Cambodia and sending the Cambodian Ambassador back to Cambodia, we will consider the level of relations further,” a government statement quoted Mr Phumtham, who is also acting prime minister, as saying.
The army, meanwhile, activated its “Chakrapong Phuwanart” emergency plan, which was last put into operation in 2011 during the conflict between the two countries over the Preah Vihear temple site.
The plan involves the 1st and 2nd army regions, which are responsible for the Central Plains and the Northeast respectively.
The army said the landmine incident occurred while soldiers were on patrol near Huai Bon in Nam Yuen district of Ubon Ratchathani at 4:55pm.
The incident resulted in injuries to five army personnel, with one soldier sustaining severe injuries to his right leg from stepping on the explosive device. The other four experienced chest tightness and tinnitus from the blast concussion. All are now being treated at Nam Yuen Hospital.
The soldier who lost his right leg was identified as Sgt Maj First Class Phichitchai Boonkorat of the 14th Infantry Regiment patrol unit.
A spokesperson said the army commander-in-chief, Gen Pana Claewplodtook, would visit the area today.
“The army seriously condemns the inhumane act which violates the principles of international humanitarianism and international agreements and occurred in the Kingdom of Thailand. It is the act of Cambodia,” it said in a statement.
“It demands Cambodia take responsibility for the incident which is considered as a serious threat to peace and stability along the border of both countries.
“The army confirms that it will use all existing mechanisms properly to protect Thai military personnel and citizens from such incidents.”
Second explosion
Yesterday’s incident was the second in the past week. A private lost his foot and two other soldiers were injured when a mine exploded in the Chong Bok area of Nam Yuen district in Ubon Ratchathani on July 16.
In the immediate aftermath of the first incident, it was not known whether the landmines were new or left over from a previous conflict. The Thai army subsequently said it had determined that the Russian-made anti-personnel mines were newly laid, and not by Thailand.
The discovery of the mines, 100 to 150 metres inside Thai territory, prompted immediate mine-clearing actions by an engineering battalion. Lt Gen Boonsin Padklang, the 2nd Army Region Commander, warned that more mines, potentially numbering in the hundreds, might remain buried in the area.
The army was placed in control of border areas after a brief skirmish in an undemarcated area in Ubon Rathchathani on May 28 in which a Cambodian soldier was killed.
Nationalist rhetoric
The latest chapter in the decades-old border dispute has prompted a series of border closings, with Cambodia blocking imports of Thai fuel, fruit and vegetables.
Online, there has been a steady stream of nationalist rhetoric, misinformation and deepfakes from both sides, while Cambodians have been accused of causing provocations while visiting a Thai temple in Surin.
The dispute has also led to a domestic political crisis, with Prime Minister Paetongtarn Shinawatra suspended pending an ethics investigation into her handling of a phone call with former Cambodian prime minister Hun Sen.
Last week, Cambodian Prime Minister Hun Manet announced that the military would start conscripting civilians next year, activating a long-dormant mandatory draft law.
He said the tensions with Thailand meant conscription was needed, and the defence budget may also be increased.