The passing of Lee Kuan Yew in March left a void in Singapore and in regional power structures. Across the region his counsel was regularly called on and his quiet moderation on important issues often proved a stabilising voice.

Lee was one of the region's key powerbrokers. Two other ageing leaders hold similar legacies in their respective countries; their eventual departure will dramatically change the political landscape.

Most notable is the Thai monarch. King Bhumipol Adulyadej, now 87, has ruled Thailand since 1946. Both legally and symbolically he is above politics and he has often stepped in to break a political deadlock. During deadly protests in 1992 he summoned the leaders of the two hostile parties and, as they kneeled before him on national TV, he brokered an end to the deadly clashes, which dispersed within hours.

But the world's longest-reigning monarch is in ailing health. With a highly politicised and contentious succession, his death will send shockwaves through Thailand's fragile politics. If there was ever a moment for further civil unrest, the fight over who will succeed him looks set to be it.

Of a different ilk, but of similar stature in Malaysia, Mahathir bin Mohamad was the country's first 'commoner' to come to power. A doctor with a local education and aristocratic ties, his ascendancy in 1981 was marked by political shrewdness, but as PM he was confrontational, and factions soon began emerging in his UMNO party. His strong-arm style allowed for two decades of rule before he stepped down in 2003. Since then Mahathir has maintained his influence in politics. When his successor, Abdullah Ahmad Badawi, fell out of favour in 2008, Mahathir withdrew his support. Badawi resigned the following year. Najib, the current PM, lives under the same pressure. Mahathir has recently campaigned for Najib's resignation. Few believe Najib can survive.

At 89, Mahathir continues to act as maestro on the country's often cacophonous political stage. When Mahathir's decades of influence over Malaysian politics comes to an end it will bring with it a dramatic change in the political landscape. 

Brunei and Cambodia also have their strongmen. But Brunei's Sultan is only 62, and Hun Sen's three decades of rule in Cambodia looks far from over.

The departure of Mahathir, King Bhumipol and Lee, three ageing powerbrokers who have stewarded the growth of their countries, will create uncertainty and leave power vacuums. Emerging leaders will find it near impossible to achieve a similar stature. The growth of the middle class and a burgeoning nouveau riche has led to the emergence of new actors (Thaksin Shinawatra is one) and a diffusion of power, making such monopolies of power more difficult. We won't see the likes of this generation of statesmen again.

Photo by Flickr user World Economic Forum.