By Jonathan Head
BBC News, Bangkok
Four months ago, the telegenic, youthful leader of the Democrats, Thailand's oldest political party, emerged in triumph from parliament, having pulled off a remarkable coup.
After years in the political wilderness, Abhisit Vejjajiva had stitched together a winning coalition, wresting control of parliament from allies of Thaksin Shinawatra for the first time in eight years.
To prove he was up to the job - he had had little ministerial experience - he set out a number of challenges he promised to meet, among them holding the biannual Asean summit meetings, which it is Thailand's turn to host, but which had been delayed by political turmoil last year.
He must be regretting that pledge now.
It made the summits, normally unexciting gatherings, but which bring together the region's most important powers, an obvious target for the aggrieved supporters of Mr Thaksin.
Disrupting an Asean summit would bring them far greater international media coverage, and undermine Mr Abhisit's claim to have restored stability.
No surprise, then, that the red-shirted protesters from the UDD (United Front for Democracy against Dictatorship), the movement that has spearheaded the campaign against this government, chose to shift their rallies from Bangkok to this month's summit venue in the seaside resort of Pattaya.
Sticks and slingshots
As this was no surprise, the government had plenty of time to prepare - 8,000 police and soldiers were deployed to block all the routes leading to the Royal Cliff Hotel, where the summit was taking place.
Mr Abhisit staked his reputation on pulling off the summit
It seemed unlikely protesters would be able to break through unless they came in massive numbers - and the crowds that eventually descended on Pattaya were never more than several thousand.
Most Asean summits are tightly choreographed affairs and demonstrations - which are rare - never get anywhere near the venue.
Yet the UDD, armed with no more than sticks and the odd slingshot, managed to push their way through police and army lines repeatedly.
At times the atmosphere seemed almost jovial, with one group of navy officers laughing and taking pictures of the red-shirts as they swarmed through.
Even right outside the gates of the hotel itself, soldiers refused to use force, and the protesters were able to barge their way in, which led to the humiliating evacuation of several Asian leaders by helicopter.
How was this possible? The prime minister had staked his reputation on pulling off this summit. He was hosting Premier Wen Jiabao of China, and Prime Minister Taro Aso of Japan, the powers everyone in this region looks up to.
Mr Abhisit had to make a grovelling phone call to apologise to Premier Wen, who, despite diplomatically saying he understood the prime minister's actions, must have been thinking: "This could never happen in China."
The government spokesman Panitan Wattanayagorn says the failings of the security forces will be investigated.
Sympathy for the UDD within the ranks of the police, a force with strong ties to Mr Thaksin, who is a former police colonel, is common knowledge.
In any case the police were badly demoralised last year after trying - and failing - to contain the protests by the rival, yellow-shirted protesters from the anti-Thaksin People's Alliance for Democracy (PAD).
But what explains the inaction of the military, a force thought to be staunchly loyal to this government?
Lack of experience in crowd control, perhaps. And there is a deep reluctance to risk bloodshed in civil disputes, ingrained in soldiers after their disastrous armed suppression of pro-democracy demonstrators back in 1992, that badly tarnished the military's reputation with the public.
But the red-shirts claim it is more than that.
"If you take off the uniforms of these people, what you find are the children of poor families," Jakrapob Penkair, one of the protest leaders told me. "So they are ideologically aligned with what the red-shirts are demanding."
The UDD has been very successful in instilling in its mainly poor and lower-middle class followers a sense that they are fighting not just for the rehabilitation of the exiled Mr Thaksin, but for social justice.
They use the language of class warfare, referring to themselves as "grass-roots people", fighting against a royalist elite that hogs the spoils of Thailand's development.
The PAD had its own successes with mass protests last year
It is an argument the Eton and Oxford-educated Mr Abhisit dismisses. Mr Thaksin, he says, must come back to Thailand and face the two-year jail sentence he received, in absentia last year, for abuses of power.
The UDD has now raised the stakes in this protracted dispute by accusing the most senior advisers to King Bhumibol Adulyadej of organising the coup that deposed Mr Thaksin in 2006.
The King himself remains popular, even revered, among opponents and supporters of Mr Thaksin alike, and his family are protected from criticism by strict lese majeste laws.
But by attacking his advisers the UDD is charging the powerful traditional elite that aligns itself closely with the monarchy of bending the rules to keep the populist Mr Thaksin out of office.
It is a potent and inflammatory message that feeds into resentment among poorer Thais over the wealth gap, and a more general anxiety felt here about the lack of clarity over the succession to King Bhumibol.
For the first four months of this year the red-shirts appeared to be a fading force, unable to ruffle the urbane Mr Abhisit, who brought calm and competent leadership back to a country with a battered economy badly in need of it.
Thaksin Shinawatra wandered the world, unable to find a secure place of exile, making occasional speeches that had little impact.
Over the past two weeks, though, he has been delivering fiery video addresses to his supporters, urging them to drive this government from office, as his allies were driven out last year.
So there was more than a hint of schadenfreude over the events in Pattaya from Jakrapob Penkair.
"I can't deny that we are pleased that they showed the disarray and fragmentation of the government forces, that Abhisit is not in control," he said.
They also show that Thailand's deep and complex political divide is still beyond the abilities of its politicians to resolve.