King Bhumibol's heir is Crown Prince Vajiralongkorn, but the laws mean any discussion of succession is extremely sensitive issue, and many aspects cannot be reported from inside the country.
In late November, it emerged that the crown prince had asked the government to strip his wife's family of their royally-bestowed name.
The move is widely expected to be a first step to divorce - the couple were already known to be estranged.
The crown prince's order followed the arrest of seven of the princess's close relatives in a purge of officials allegedly involved in corruption.