By Jonathan Head
BBC News, Bangkok
Both Thailand and Cambodia retain troops at the hill-top temple
A week after the controversial listing of the ancient Preah Vihear temple as a World Heritage Site, the dispute that has flared up between Thailand and Cambodia is still causing tension.
The 11th-Century Hindu temple lies along the border between the two countries, but in 1962 the International Court of Justice judged that it belonged to Cambodia.
However the land surrounding the temple is still disputed, and the only practical access is from Thailand.
The issue has stirred up nationalist emotions in an already sensitive political climate in both countries.
Early on Tuesday three Thai protesters crossed into the temple - which remains closed - and were detained for a short time by Cambodian troops.
The Cambodian authorities also say 40 Thai soldiers crossed into their territory briefly, although they are putting this down to confusion over the precise line of the border.
For both sides there is more at stake than a temple.
Cambodia is preoccupied with a hard-fought general election campaign, in which Prime Minister Hun Sen aims to extend his more than two decades in power.
Last week he encouraged thousands of Cambodians to join a rowdy celebration of the temple's new international status in the capital, Phnom Penh.
The Unesco World Heritage listing sparked celebrations in Cambodia
In Thailand feelings are running even higher; the government elected last December was already floundering under a combined assault by street demonstrators, unfavourable court verdicts and the parliamentary opposition.
Its opponents have accused it of incompetence, and of being led by nominees of former Prime Minister Thaksin Shinawatra, who was deposed by a coup in September 2006.
Now the government is being attacked for selling out the country over Preah Vihear, because it initially supported Cambodia's bid to list the temple.
One of Thailand's top courts judged that decision to be unconstitutional, as it was in effect a treaty which needed parliamentary approval, and it has barred the government from offering any further co-operation with Cambodia.
As a result Foreign Minister Noppodol Pattama was forced to resign last week, one of three ministers to lose his job over the past two months.
Opposition from elite
The volatile state of Thai politics is the principal reason the row has blown up.
Thai society is still deeply polarised between those who support Mr Thaksin, and want him to stage a political comeback, and those who loathed his leadership style and mistrust the motives of the government, which is led by his party.
The fact that before being appointed foreign minister, Mr Noppodol had been Mr Thaksin's chief lawyer made his position particularly vulnerable.
His critics accuse him of putting his former client's business interests in Cambodia before the country's interests over the temple, something he has strongly denied.
That suspicion harks back to the five-and-a-half years Thaksin Shinawatra was in office. As an immensely wealthy and successful businessman himself, he promoted his can-do ethos around the country, especially in poorer rural areas.
He believed in the global marketplace, and in exposing Thais to its risks and opportunities. He pushed hard to privatise state-owned industries and get free trade agreements with as many countries as he could.
Inevitably he provoked opposition from those who felt they would lose out, or from those who felt he cared more about making money than about Thailand's traditions and interests.
The most vehement opposition to the Preah Vihear World Heritage bid comes from the same groups who objected to many of Mr Thaksin's policies: the traditional, royalist and aristocratic elite and elements of the Bangkok middle class.
But there are also genuine historical grievances at play.
The international court decision awarding Preah Vihear to Cambodia in 1962 was not unanimous. It rested largely on Thailand's failure to protest against the French-drawn border line in the decades before.
At the time it was mapped, a hundred years ago, Thailand had few skilled cartographers of its own.
The temple sits on cliffs which form the border between the two countries
The French colonial cartographers were supposed to draw the border along the forested edge of the Dangret Escarpment, but they veered in a few hundred metres to put the temple on the Cambodian side. It is not clear why the Thais did not object then.
But it is worth remembering that in 1941 Thailand fought its only war of the 20th Century with French colonial forces over where the border with Cambodia should lie. A huge monument in the centre of Bangkok still commemorates that conflict.
At different periods in the past Thai and Khmer empires have vied for dominance in the region; the town next to the famous Khmer ruins at Angkor Wat is Siem Reap, which means "Siam [Thailand] flattened".
Khmer-style temples like Preah Vihear still dot much of Thailand's north-east.
That historical rivalry still resonates today. Only five years ago the Thai embassy in Phnom Penh was burned down by an angry mob after a Thai actress was wrongly quoted as saying Angkor Wat should belong to Thailand.
As it awaited news of the listing of Preah Vihear as a World Heritage site, the Cambodian government took the precaution of reinforcing security around the re-built Thai embassy.