Twenty-five years after downgrading ties with Bangkok, Saudi Arabia is offering an olive branch to "normalise'' its relationship with Thailand.
The offer, however, depends on the outcome of an appeal involving a long-running murder case.
The two countries mark six decades of diplomacy next year. After withdrawing its charge d'affaires to Thailand a year ago in protest at the way the case was going, the Gulf state has now sent him back in the hope his presence can help bring about a favourable ending to the saga.
Saudi Arabia's appeal to normalise ties is conditional on Bangkok providing justice to the family of a Saudi businessman murdered in 1990. The Criminal Court acquitted five Thai defendants in the case last year, prompting the Saudi protest.
Saudi Arabia has now sent its charge d'affaires to Thailand, Abdalelah Mohammed A Alsheaiby, back to Bangkok in the hope a forthcoming appeal against that verdict will find against the men.
Riyadh has not specifically called for the Thais accused of the murder to have their acquittals overturned. The wish is couched in more diplomatic language, and carries with it the prospect that trade and tourism ties will improve. Currently they are held back by trade sanctions and a travel ban.
Speaking from the Saudi embassy in Sathon Road, Mr Alsheaiby said Saudi Arabia sent him back to Bangkok last month because "Riyadh would like to follow up on positive signs from the Thai side".
Among those signs was the creation of an inter-agency body chaired by a deputy permanent secretary of the Foreign Ministry to "clear issues" hindering Saudi-Thai relations, he said. "I plead to all sides to work toward an improvement in our bilateral relations so the history of our long ties together will not be futile," Mr Alsheaiby told the Bangkok Post.
The fifth charge d'affaires since the 1990 diplomatic downgrade said many Thais and Saudis want to see warmer ties. "My mission is to communicate and see to the final resolution of this court case. The ball is in the Thai court now and Saudi Arabia is ready to celebrate together," he said as Riyadh awaits the verdict from the Court of Appeal, following last year's ruling by the Court of First Instance.
- Related: Haj pilgrim in Yala may have Mers
On March 31, 2014, the Criminal Court acquitted all five defendants including Pol Lt Gen Somkid Boonthanom, a former police inspector-general and a younger brother of a 2006 coup-maker, of the abduction and murder of Mohammad al-Ruwaili in February 1990, a businessman who had close links to the Saudi government and the royal family.
The acquittals shocked the Ruwaili family, two of whom flew in to hear the verdict, and the Saudi government. Three months later, the Saudi King recalled the charge d'affaires to Riyadh.
Ruwaili's disappearance and presumed murder followed the separate murders of four diplomats in January 1989 and February 1990. Police initially arrested Thai-Muslim men and charged them with the murders, but the Supreme Court dismissed the cases against the defendants. The Department of Special Investigation (DSI) concluded that the murders of the diplomats were linked to "sectarian disputes".
Panitan Wattanayagorn, then a deputy secretary-general for the Abhisit Vejjajiva government, told US assistant secretary for political-military affairs Andrew Shapiro in 2010 that the four diplomats had been killed by Hezbollah, supposedly in retribution for bungled attempts by the Saudi government to assassinate Hezbollah operatives.
But Mr Alsheaiby compared the Saudi diplomat murder cases to the brutal killings of two British nationals on Koh Tao, in which two suspects were arrested and are awaiting trial. "They were able to find the [alleged] culprits right after that island murder," he said.
"I'm amazed and am wondering why Thai authorities can find culprits for [the murders of] British nationals but not for us," he said, adding the Ruwaili case was the only remaining chance for justice. "Whether we can restore good ties between us relies solely on this case."
The Ruwaili family petitioned His Majesty the King and appealed to the Appeal Court. "We will proceed through to the end [the highest court]. I believe the Thai government has good intentions to normalise relations. But the restoration will have to be done without the rights of our citizens being infringed upon," Mr Alsheaiby said.
Several businesses are keen to invest in Thailand, but they have been prohibited because of economic sanctions, he said. The Saudi low-cost airline, Flynas, is keen to launch a route between Jeddah and Bangkok to tap the market for tourists and Haj-Umrah pilgrims.
Currently, most flights between Saudi Arabia and Southeast Asia are via the Philippines and Indonesia as they supply workers to the Saudis.
"Once relations are restored the Saudi private sector would like to hire Thais rather than other nationals," Mr Alsheaiby said.
Before the downgrade and sanctions, up to 500,000 Thais worked in Saudi Arabia. Now perhaps just 100 are there. Thousands of students once studied in Saudi Arabia, but now only 300 do.