The Blue Diamond Affair

A theft from a royal palace

In 1989 Kriangkrai Techamong, a Thai man working as a cleaner at the Riyadh palace of Prince Faisal bin Fahd, the eldest son of King Fahd of Saudi Arabia, removed a huge quantity of jewellery and gems over a period of several weeks and smuggled them to Thailand. Some reports call him a gardener. The loot was said to weigh more than 90 kilograms and is usually valued at about 20 million US dollars. Its most famous piece was a rare blue diamond of around 50 carats, which gave the scandal its name.

Kriangkrai was arrested in Thailand in 1990 after confessing and was given a five-year prison sentence. Sources disagree on how long he actually served: one regional newspaper says less than three years, while wire reports say five. He had already sold many of the stones before his arrest, and in 2016 he became a Buddhist monk.

Fakes, missing stones and suspicion

Thai police recovered part of the collection and sent it back to Riyadh, but Saudi officials said that most of the returned pieces were imitations. The blue diamond itself has never been located. Saudi Arabia accused the police of bungling the inquiry, and there were widespread allegations that senior officers had kept genuine items. No court has established that any such swap took place.

Diplomats killed and a businessman vanishes

The affair overlapped with a wave of violence against Saudi officials in Bangkok. A Saudi diplomat was shot dead in the Silom area on 4 January 1989, and on 1 February 1990 three more were killed in Yannawa district. Saudi-Iranian tensions had led to attacks on Saudi diplomats in several countries in that period. Saudi Arabia has long complained that Thailand never brought the killers to justice.

Soon afterwards, in February 1990, Mohammad al-Ruwaili, a Saudi businessman related to the royal family, disappeared in Bangkok. He had been sent to look into the theft and also worked as a broker for Thai labour. Accounts differ on the gap, with most reports saying he vanished days after the three diplomats were killed and one saying about a month. His remains have never been found.

The al-Ruwaili prosecution

Nearly two decades later, on 24 November 2009, five men who had been police officers in south Bangkok surrendered to the Department of Special Investigation and were charged over al-Ruwaili's abduction and murder. They were Pol Lt Gen Somkid Boonthanom, Pol Col Sorarak Jusanit, Pol Col Praphas Piyamongkol, Pol Lt Col Suradej Udomdee and Pol Sgt Maj Prasong Thorrang. Prosecutors alleged that the businessman had been detained and questioned about the diplomats' deaths and then killed.

On 31 March 2014 the Criminal Court acquitted all five for lack of evidence. The prosecution's key witness, a police officer, had not testified in person, and the court found his written statement insufficient. Saudi Arabia publicly objected to the replacement of the presiding judge shortly before the verdict. The Appeal Court upheld the acquittals on 3 May 2016, and the Supreme Court confirmed them in 2019. The five men are therefore legally innocent.

A separate conviction

One episode linked to the hunt for the gems did end in a conviction. In 1994 the wife and seven-year-old son of gem dealer Santhi Sithanakan were abducted by a team under Police Lieutenant General Chalor Kerdthes and later found dead in a car outside Bangkok, staged to look like an accident. Chalor was sentenced to death, the sentence was commuted, and he was freed in 2013 at the age of 70 after almost 20 years in prison.

Three decades of frozen ties and the thaw

Saudi Arabia downgraded relations with Thailand, stopped sending an ambassador and restricted travel. Before the theft as many as 200,000 Thais worked in the kingdom; that number later fell to a few thousand. Trade in oil, auto parts, seafood and rice continued.

On 25 January 2022, Prime Minister Prayut Chan-o-cha met Crown Prince Mohammed bin Salman in Diriyah, near Riyadh, on the first visit to the kingdom by a Thai premier in more than 30 years. The two sides announced the full restoration of relations and agreed to exchange ambassadors. Thailand's government spokesman said Prayut had expressed regret over the events of 1989 and 1990 and pledged to reopen the investigations if new evidence emerged. The crown prince visited Thailand in November 2022.

Where things stand

Normalisation has continued. Around 200,000 Saudis visited Thailand in 2023, and from mid-2024 Saudi visitors could stay up to 60 days without a visa. The criminal questions, however, remain open: the blue diamond is still missing, the four diplomats' killings remain unsolved, and al-Ruwaili's fate has never been legally resolved. Crime by Region lists the case as unsolved. For Thailand, the affair is a rare example of how allegations of police misconduct in one theft inquiry cost the country a major labour market and a key diplomatic relationship for a generation.