Authorities in Thailand have charged two people with spreading rumours about the ill health of King Bhumibol Adulyadej and contributing to a sudden plunge in Thai share prices last month.

The man and woman, both Thais with connections to the financial industry, face up to five years in jail for allegedly breaking Thailand’s computer crime law. One of the suspects, who were released yesterday on bail of 100,000 baht (£1,800), insisted that her crime amounted to no more than translating into Thai an article about the king’s health from a foreign news agency.

Teeranun Wipuchanin, a 43-year old former executive with the Swiss bank UBS, and Katha Pajajiriyapong, 37, an employee of a Thai securities company, were arrested separately on Sunday for “feeding untrue information through a computer system which undermined the security of the nation”, according to Bangkok police. Speaking to reporters after her arrest, Ms Teeranun suggested that she had done no more than react to the continuing fall in the markets.

“What I've done was translating documents from [the] foreign media [organisation] Bloomberg,” she said. “I got it from [the] internet. Everybody on that day wanted to know what caused the market to fall. The stock market had already dropped and we did the translation in the evening.”

Ms Teeranun was arrested at Suvarnabhumi airport in Bangkok after returning from Vienna. Her notebook computer, digital camera and mobile phone were seized, as well as a computer at her house. She admitted posting the translated article at prachathai.com, a website that challenges the lèse-majesté law and the legitimacy of a military coup in 2006.

Thailand’s Securities and Exchange Commission said that it was seeking trading information on accounts at overseas branches of two Swiss brokerages, Credit Suisse in Hong Kong and UBS in Singapore, as well as one account in Thailand. The implication was that the rumours were used deliberately to manipulate the value of shares for profit.

The arrests serve to underline the intense sensitivity of information about the personal life of 81-year-old King Bhumibol and his family, and the uncertainty that many people feel about the future of Thailand after his death. He was admitted to Bangkok’s Siriraj Hospital on September 19, reportedly suffering from mild fever and loss of appetite.

The regular reports on his health were vague and his doctors appear to have been late in owning up to the exact nature of his illness, which appears to have been pneumonia. It was more than a month before the King was shown on Thai television, apparently frail but healthy, being pushed about the hospital in a wheelchair. He remains in hospital but is said to be regaining his strength after making a recovery.

On October 14 and 15, the Stock Exchange of Thailand fell by a total of 7.2 per cent, and at one point by more than 8 per cent, because of rumours that the king’s condition was grave and fears of the political instability that could follow his death.

Constitutionally, King Bhumibol is no more than a symbol of the state but in practice he is one of the most influential men in the country and the focus of an intense personality cult. He is protected by a harsh lèse-majesté law that punishes any perceived “insult” to the monarchy with a prison sentence of up to 15 years.

He rarely makes direct interventions into politics but when in the past he has appealed for national unity his words have carried a moral authority that few question. In a time of great political turmoil in Thailand, which has been rocked by violent clashes between followers of the deposed Prime Minister Thaksin Shinawatra, and their “Yellow Shirt” opponents, he is regarded as a precious symbol of stability.

This respect has not been inherited by his son and heir apparent, the Crown Prince Maha Vajiralongkorn. Like his father, the Crown Prince is protected by the lèse-majesté laws, which has stifled reliable reporting of the many rumours about his private life. An Australian writer, Harry Nicolaides, spent five months in prison for a novel that briefly referred to the “romantic entanglements and intrigues” of the Crown Prince, before eventually receiving a royal pardon.

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