Thailand's new King Rama X is the 10th in a dynasty that dates back to 1782, but he will be judged by how he measures up to his revered father, who steadily steered his country into modern times in a 70-year reign.
Rama X - who also was given the formal title "His Majesty King Maha Vajiralongkorn Bodindradebayavarankun" today - had been the heir apparent since 1972, when King Bhumibol Adulyadej named him as his successor.
Bhumibol died on October 13 at age 88 after years of ill health.
Now the 64-year-old Vajiralongkorn, the second child and only son of Bhumibol and Queen Sirikit, faces the challenge of sustaining a constitutional monarchy.
It's a monarchy in a politically troubled land - led by the military since 2014 - that's seeking to earn the same respect King Rama X's hard-working father had.
The public has long speculated about Vajiralongkorn's finances, hot temper and other matters.
Three failed marriages are a matter of public record.
As crown prince and now as king, Vajiralongkorn has been protected by a Thai law mandating a prison term of three to 15 years for anyone found guilty of the loosely defined crime of insulting the monarchy.
Prosecutions under the lese majeste law, and blocking of internet sites deemed insulting to the royal family, have grown more common in recent years.
Although he attended the requisite royal ceremonies and in recent years filled in for his father for some ceremonial and diplomatic duties, the prince is generally a private figure, visibly ill at ease in most public settings.
His three sisters and first wife often appear on nightly television broadcasts of royal news, attending social functions and carrying out good works that burnish the monarchy's reputation.
Vajiralongkorn's appearances have been less frequent.
While all the siblings travel abroad frequently, his sisters usually are promoting their homeland in one manner or another.
The prince's activities are usually personal and unpublicized, outside of the occasional tabloid story in the country he is visiting.
He has spent much of his time at residences in Germany, and returned from a stay there just ahead of becoming king today.
Thailand 's new king Maha Vajiralongkorn Bodindradebayavarangkun speaking after acceptance throne at Dusit Palace.
Source: Associated Press
In 2015, he made two high-profile public appearances in Thailand, leading thousands of people in mass bicycling events to mark the birthdays of his mother and father.
Many saw the events as an attempt to polish his image in preparation for his eventual installation as king.
Born on July 28, 1952, the prince was accorded the kind of smothering attention one would expect from growing up in a palace.