"It's a complicated situation," said Patrick Jory, an expert on the Thai monarchy at the University of Queensland.
Bhumibol was not formally crowned until May 1950, more than four years after his brother, King Ananda Mahidol was found dead of a gunshot wound to the head
under mysterious circumstances.
The Crown Prince
Under the 1924 Palace Law of Succession, the Thai king has absolute power to designate his successor.
Bhumibol's only son, Maha Vajiralongkorn, was officially appointed crown prince and heir apparent on December 28, 1972, at the age of 20.
In the event of the king's death, parliament should invite the designated heir to immediately assume the throne. However, Prime Minister Prayut Chan-o-cha said Thursday that Vajiralongkorn "needs time to jointly mourn with the Thai people" before he succeeds his father.
While there is little doubt that Vajiralongkorn will become king, Jory said it was "surprising" that he did not do so immediately, and warned that a prolonged period of uncertainty could hit the country's stock market
The Privy Council
Until Vajiralongkorn does assume the throne, becoming King Rama X, the president of the Privy Council serves as temporary regent, in accordance with the Thai constitution
The Privy Council is an elite body of advisers, appointed by the king, which has significant powers with regard to royal appointments and the law of succession.
King Bhumibol's last council, which remains in place until Vajiralongkorn appoints his own, is headed by former Prime Minister and army general Prem Tinsulanonda.
"(Prem) has been a key player since the 1980s and was the king's right hand man," said Jory.
In 2006, Prem was accused
of masterminding the coup that ousted democratically-elected Prime Minister Thaksin Shinawatra. He denied the claims.
Other members of the council include fellow former prime ministers Thanin Kraivichien and Surayud Chulanot, and Chalit Pukbhasuk, a former acting chairman of the Council for National Security, the junta that overthrew Thaksin.
When Vajiralongkorn does assume the throne, he is likely to replace the council with his own supporters, Jory said.
As a constitutional monarchy, power in Thailand officially lies with the government, with the king as head of state.
Since seizing power in a 2014 coup
, a military junta has been in control, headed by Prime Minister and retired Royal Thai Army commander in chief Prayut Chan-o-cha.
For two years following the coup, the junta ruled Thailand
through a combination of martial law and emergency laws passed "to curb acts deemed harmful to national peace and stability."
In August, Thais voted to approve a new constitution that entrenched "the power of the military and traditional elite," according
to the Institute of Southeast Asian Studies (ISEAS), a Singapore-based research organization.
Prayut told CNN last year
that "our country must be fully democratic," and denied that he was trying to delay or meddle in the return to civilian rule.
However, ISEAS warned that thanks to sweeping new powers granted the military by the new constitution "the traditional elites would in effect have design new mechanisms to seize power without resorting to a military coup."