MIGHTY KHMER KINGS ruled vast swathes of South East Asia from around AD1000, power waxing and waning over the centuries. Their neighbours, the Cham or Siamese or Vietnamese pushed back, and the capital made repeated changed, especially in the latter part of the millenium.
The most famous modern member of the royal family was King Norodom Sihanouk. He became King in 1941, then at various times, Prime Minister, Head of State, rebel, figurehead, prisoner in his own palace, leader of government in exile, and in 1993, King again.
The royal family is bigger than your average family, and continues to play a role in politics.