Thailand's Crown Prince has divorced his wife in a dramatic fall from grace for a senior princess that comes at a time of heightened anxiety over the health of Thailand's revered but ailing monarch.

A statement published by the palace overnight in the Royal Gazette said Princess Srirasmi had relinquished her royal status, a move that ends her 13-year marriage to Crown Prince Maha Vajiralongkorn.

The announcement comes after a string of the princess' relatives were arrested in a high-profile corruption scandal that has sent shockwaves through Thailand's elite.

"The king has granted permission to announce that Princess Srirasmi, the wife of Crown Prince Maha Vajiralongkorn, has informed in a written document that she has resigned from her royal status," the palace said in its short statement.

Analysts said the Crown Prince's split from his wife will deepen fears for the monarchy's future as Thailand's 87-year-old monarch King Bhumibol Adulyadej enters the twilight of his reign.

In May, Thailand's military seized power after months of violent street protests saying it needed to do so to protect the monarchy and restore order to the politically divided nation.

The king -- who is revered by many Thais as a semi-divine figure -- has been largely confined to hospital this year and pulled out of plans to hold a public audience earlier this month during his birthday celebrations.

Srirasmi married the Crown Prince in 2001 and had been expected to become queen. The couple have a son who was thought to be Prince Vajiralongkorn's most likely heir.

"This announcement will add a greater sense of uncertainty and anxiety among Thais over the future of their monarchy -- not just with the current generation, but with later generations too," Pavin Chachavalpongpun, a Thai expert at Japan's Kyoto University, told AFP.


'Rumours and arrests'

Thailand has been awash with rumours of Srirasmi's fate for weeks after a slew of her relatives were caught up in a widening police corruption scandal.

Several high profile figures have been arrested including a host of senior policemen and military officers, while one of Thailand's richest men is on the run from police on charges relating to the probe.

But reportable facts on Srirasmi's status were scant.

The country's monarchy is protected by some of the world's strictest lese majeste laws. Both local and international media must heavily self-censor when covering the country's royal family.

The first indications that the 43-year-old's royal status could be in doubt came earlier this month when the Crown Prince announced that members of her family had been forbidden from using the surname "Akkharapongpricha".

At least three relatives with that surname were arrested in the corruption scandal, and the name represents an honorific title given to some of Srirasmi's family following her marriage to the prince.

Many of the more than 20 detained have been charged for defaming the monarchy, with police saying they had made "false claims" about their relationship to a royal to justify committing crimes that allegedly ranged from running illegal casinos to oil smuggling, kidnapping and extortion.

Under section 112 of Thailand's criminal code, anyone convicted of defaming, insulting or threatening the king, queen, heir or regent faces between three and 15 years in prison on each count.

Even repeating details of the charges could mean breaking the law.

In recent days there were increasing signals Srirasmi was no longer part of the royal family.

In an unusual break from tradition, there was no mention of her in the royal household news broadcasts on December 9, her birthday.

The next day she disappeared from the opening sequence of the nightly royal news broadcasts, which features portraits of all the kingdom's senior royals.

The princess was last seen in public on December 6 when she presided over the 9th anniversary of her pet project, an organisation called "The Family Bond Project".

The report on the Ministry of Education website says the project "aims to promote and strengthen love and learning between all family members".