A 58-year-old passenger who died on a Tigerair flight from Chiang Mai on Tuesday had been hospitalised before the flight, according to media reports.
Chinese evening daily Lianhe Wanbao said he needed to use a wheelchair and had been warded at a hospital in Chiang Mai, where he was visiting with family. Family members slept on the floor in the hospital while he was there, said the report.
According to Lianhe Wanbao, his child had updated a Facebook album on Jan 12, which was accompanied by a post.
It said: "We learn something from everyone who passes through our lives.. Some lessons are painful, some are painless.. but all are priceless." It ended with the words: "Fulfilling Papa's wishes."
The man, identified as Mr Seet Ngow Chai by Thai news website Khaosod, was travelling with family members back to Singapore on Flight TR2177, when he collapsed on board.
The pilot then diverted the plane to Suvarnabhumi Airport in Bangkok for medical help, but Mr Seet could not be saved.
Broadcaster Thai PBS said on Wednesday that his wife, who is Thai, had told airport officials her husband was suffering from a chronic illness. It was not made clear what that was.
The Thai police are reported to be carrying out investigations.
Tigerair said in a statement that its immediate concern is the man's next-of-kin and that it is doing what it can to assist them.
The flight arrived back at Changi Airport close to midnight on Tuesday, more than six hours after it had departed from Chiang Mai.