Thai police have arrested a fourth suspect in the weapons smuggling case linked to a Cambodian immigration officer, according to Thai media, while a senior Cambodian Defence Ministry official said yesterday that any suggestions that the weapons came from Cambodia’s military arsenal had been ruled out.

The developments are the latest in the case which emerged on June 3 when a Thai air force officer crashed a pickup truck just over the Cambodian border in Thailand’s Trat province while transporting a weapons cache that included 29 AK-47s, four machine guns, explosives and ammunition.

According to Thai news station Nation TV, Thai authorities on July 10 arrested police Lieutenant Sima Ketep at his home in Lopburi province, more than 400 kilometres northwest of the crash site in Trat, which borders Koh Kong province.

The station said Sima has been charged with illegal weapons possession alongside the three other suspects in the case – the air force officer, Pakhin Detphong, Thai national Jakkapong Krairiang and Cambodian immigration officer Leang Piseth, who is a relative by marriage of both Defence Minister Tea Banh and former Koh Kong Provincial Governor Bun Leut.

The police have alleged that Piseth – who was arrested with Krairiang in the hours after the crash as the pair drove towards the Cambodian border – smuggled the guns to Thailand the day before the crash.

Sima was named by his co-accused as the “facilitator” of the arms trafficking, but has denied involvement, according to Nation TV, which also reported that Sima had previously been accused of weapons trading but that the case was dropped.

The weapons found on June 3 were destined for ethnic Karen rebels in Myanmar, according to Thai police, and Interior Minister Sar Kheng last month confirmed that the cache had been transported from Koh Kong into Thailand without passing through the province’s official international checkpoint.

Kheng vowed an investigation into the origin of the weapons. Interior Ministry and National Police representatives could not be reached yesterday to discuss the progress of the probe.

However, the director general of the Defence Ministry’s technical material department, General Chao Phirun, said that his department had undertaken a thorough check of weapons records for bases in the area – as well as of the Defence Ministry’s warehouse – and that no guns were missing.

“After the news about the smuggling, I checked. We found that no weapons were lost. There was no loss from the military side,” said Phirun, who also dismissed any other connections between the alleged trafficking and the military. “There is no link to that activity, we have already investigated it.”

Following decades of civil war, the European Union and Japan funded a six-year programme starting in 1999 that led to more than 140,000 weapons destroyed and the military’s remaining arsenal registered and stored in upgraded facilities. Phirun said that the strict gun-storing measures were still in place.