A few months ago, Cambodian Premier Hun Sen seemed to revel in his role as host of a regional summit; the appearance of top leaders in Phnom Penh - Chinese Prime Minister Zhu Rongji among them - marked one more step away from controversy and towards legitimisation as a statesman.
The summit came amid a spell of relative economic, diplomatic and political stability in Southeast Asia, one which had allowed it to focus on new challenges, from the threat of terrorism to China's growing economic might. A few months on, events in Cambodia have provided a sharp reminder of the ancient passions which stalk the region and can threaten stability at any time.
That Cambodians jealously guard their sovereignty over the Angkor temples - at the heart of 1,000 years of dispute with Thailand - is nothing new. That a new generation of Cambodians, fuelled by Internet gossip and newspaper rumour, can riot and torch the Thai embassy and Thai-owned businesses on the strength of the alleged remarks of a Thai actress questioning that sovereignty is more striking.
The night of violence that spread across Phnom Penh last Wednesday did not reflect well on Hun Sen nor on his government. Earlier in the week, and despite the doubts already raised about the accuracy of reports of the actress' remarks, Hun Sen seemed keen to pander to public sentiment.
He went on national radio to denounce the actress, Sunavant Kongying, labelling her a thief whose life 'is not even equal to a patch of grass around Angkor Wat'. The night of mob violence that followed seemed to catch his team by surprise. A leader known for his strong-arm rule appeared neither in control nor in touch.
Thais will not easily forget that their ambassador fled for his life or that protesters desecrated a portrait of their revered King Bhumibol Adulyadej. If Hun Sen aspires to the status of a statesman he must mend fences and ensure the quick resumption of the tourism trade which benefits both countries. The opportunity presented by the visit to Bangkok on Tuesday of his foreign minister, Hor Namhong, must be fully grasped.
Old tensions may still simmer, but Southeast Asia has shown it can move beyond them. Now is the time for Hun Sen to show he is a leader worthy of a modern region.