Cambodia-Vietnam relations have long been turbulent. Occupation, conflict and political meddling have been hallmarks of the relationship, and disagreement about the border has long been a bone of contention. Last year a group of 600 protesters burned a Vietnamese flag outside the embassy in Phnom Penh, earning a strong rebuke from Hanoi.

Tensions have continued to simmer since. In June, Cambodian activists clashed with Vietnamese villagers in Svay Rieng province, which lies between Phnom Penh and Ho Chi Minh City, while Cambodian police looked on (raw footage here; read an excellent article on anti-Vietnamese sentiment in Cambodia here). This week, tensions have also bubbled over around maritime borders.

Both Hanoi and Phnom Penh are seeking a speedy resolution to demarcate the problematic land border. The process is 80% complete. Yet as it draws closer to being finalised there is an increasing risk of further problems. Following a three-day meeting in early July, the two parties agreed to complete the demarcation 'very soon'.

But given the highly politicised nature of the issue, that deadline may prove difficult to meet. The border dispute is testing Cambodia's Prime Minister Hun Sen. Memories are long and many Cambodians still see him as a Vietnamese puppet (he was part of the the government installed  by Hanoi following the Vietnamese overthrow of the Khmer Rouge in 1979). Anger will grow if the border deal isn't seen as favourable. 

Sam Rainsy, the opposition leader, has for almost two decades employed xenophobic rhetoric against the Vietnamese.

In 1998 he campaigned on a ticket to expel the yuon, a derogatory Khmer term used for the Vietnamese. Little has changed since. In 2009 Rainsy led a group of activists on a visit to disputed territory along the Vietnamese border where they uprooted a demarcation post. This populist move saw him sentenced to two years in jail, after which he fled into self-exile until in 2013, when he received a royal pardon, returning to contest the elections. His tactics haven't changed. Disputes with Vietnam are the oxygen for much of his and the Cambodian National Rescue Party's popularity. 

The CNRP claims that current negotiations over demarcation are using Vietnamese maps and are thus unfavourable to Cambodia. Such claims play well with many Cambodians, and Hun Sen has looked to quell such assertions by requesting maps from the UN drawn up during French rule.

Worryingly, decades of skirmishes between Cambodia and Thailand around the disputed territory of Preah Vihear Temple may indicate to some Cambodians that violence gets results. This concern is exacerbated by the fact that Cambodia is undergoing a period of heightened political uncertainty. The 2013 elections left Hun Sen weakened, with the opposition nearly doubling its share of seats in the national assembly. Months of subsequent political deadlock resulted in concessions being granted to the CNRP. The Opposition has increased its influence in politics and is frustrating Hun Sen's usually firm control, and the border issue could further strengthen support for the CNRP. Coupled with persistent grievances toward deep-rooted corruption, inequality and the enrichment of the elites that support Hun Sen, this could create a perfect storm for the ruling Cambodian People's Party.

Hun Sen, a master strategist who has maintained a grip on power for three decades, has recently made moves to strengthen his own hand. In July, 11 opposition activists were jailed for 'insurrection' for their role in last year's protests, and a law that will restrict the operations of NGOs (and inhibit their criticisms of government) was passed.

In recent weeks Hun Sen and his defence minister have warned the military to be vigilant and ready to suppress any attempt at a 'colour revolution'. Much of the oxygen for such a 'revolution' could come from the border dispute, particularly if there is anger over any perceived ceding of territory to Vietnam.

Phnom Penh isn't the only party that wants to see the back of the demarcation process.

For Hanoi, resolving border disputes is one way of hitting back at what it feels is its growing isolation. Both Cambodia and Laos are increasingly influenced by Beijing, thanks to significant Chinese investment. Hanoi worries that Cambodia, which many see as a quasi-vassal state of China, could be manipulated to create problems along the border with Vietnam. Such concerns have lingered since 2012 when Phnom Penh prevented any ASEAN unity against Chinese assertiveness in the South China Sea. Vietnam worries that Phnom Penh could escalate the border dispute as a distraction from any incident with China in the South China Sea. In such a situation, Hanoi could be in hot conflict with its two biggest neighbours on two very different fronts.

Hanoi's sense of isolation has no doubt factored into its attempts in recent years to develop a more proactive and open foreign policy characterised by a long-held motto of 'fewer enemies, more friends'. Most telling is the recent warming of relations with the US – last month's visit to Washington by the general secretary of the Communist Party of Vietnam was a first. 

ASEAN, the UN and other governments should support and indeed insist on the speedy resolution of the border dispute. While it could be settled in the Hague, much like the 2013 settlement of the Preah Vihear case, this would be a lengthy process which would ignite more nationalism. And Hun Sen is all too aware that the longer the process drags on, the more it plays into the hands of the opposition ahead of promised elections in 2018. For its part, Hanoi would be happier with the current Hun Sen Government than an unknown and seemingly anti-Vietnamese one in Phnom Penh,  though it would no doubt prefer a government less influenced by Beijing.

How the border disputes are resolved will be an important indicator of Cambodia's stability and how Vietnam and Cambodia can work together on an issue of mutual interest.

Photo courtesy of Flickr user Emad Ghazipura.