The pivotal position of the monarchy in Thailand's political order makes the succession a sensitive issue
The 1924 Palace Succession Law, enshrined in subsequent constitutions, follows the principle of primogeniture, meaning Crown Prince Vajiralongkorn is the designated heir to King Bhumibol, and his own sons should inherit the throne after him, ranked by age.
However, the law also gives reigning kings considerable sway in choosing their own successor - and an amendment to the constitution now allows the possibility of a female successor.
Does the crown prince have any other male children?