Profile: Crown Prince Vajiralongkorn
Crown Prince Maha Vajiralongkorn will inherit the Thai throne, the prime minister has said, following the death of his father King Bhumibol Adulyadej.
The 64-year-old, who is the king's only son, will succeed a much-loved monarch, assuming a role many in Thailand regard as semi-divine.
But there are fears the new king will not have the same authority as his father.
The crown prince's colourful lifestyle and the country's current political instability mean a smooth succession is not guaranteed.
Thailand has strict lese majeste laws which protect the royal family from insult or threat. They have largely shielded the monarchy, including the crown prince, from public view or scrutiny.
Most ordinary Thais know only a few details about who he is and how he lives his life.
Crown Prince Vajiralongkorn was born on 28 July 1952 in Bangkok, the second of four children of King Bhumibol and Queen Sirikit.
He studied at prestigious schools in England and Australia before undergoing military training in Australia.
A military officer and pilot, his lifestyle and behaviour have at times been marked by scandal.
He has been married three times, with his second and third marriages ending in controversial and very public ways.
After his second marriage, he severed all ties to his former wife and disowned four children he had with her.
He is thought to spend much of his time abroad.
In recent years, the crown prince has tried to improve his profile with the Thai public.
Last year, he led thousands of cyclists through the streets of Bangkok in two bike rides in honour of his parents.
He came across as a loving and dutiful son - an image he will be hoping to project over the coming months.
His public image is important because the king is traditionally seen as a guiding force in politics.
With the military in control of the country after a coup two years ago, and Thai society politically polarised, some fear months of instability.