All four once-exiled sons of the king of Thailand have been allowed to return to their home country for the first time in nearly 30 years – a development expected to be closely watched as the rich 72-year-old monarch is yet to officially endorse an heir.

Two of the princes had previously travelled to the country, but images on social media of the arrival on Friday of the eldest and youngest sons from the king’s doomed second marriage marks a new twist in a fascinating but secretive succession drama.

Its outcome will shape the fate of a multibillion-dollar........

© The Sydney Morning Herald