An exiled critic of the country's military and monarchy said he was attacked in his home in Japan last month and believes Thai authorities were behind the incident, an accusation that was ridiculed by the kingdom's army chief.
Pavin Chachavalpongpun, a 48-year-old associate professor at Kyoto University, said he was asleep with his partner when a man broke into their home last month at about 4am and sprayed the couple with a substance that burned their skin.
Neither was seriously hurt, but Mr Pavin said they have been told by police not to return home. Japanese police confirmed they were investigating a July 8 incident in which a Thai man was sprayed in his house.
"The attacker clearly wanted to intimidate," said Mr Pavin, adding that he had no personal disputes that could have been behind the attack. "The doctor said the chemical was not deadly, but said that the burning sensation will stay for quite some time."
A prominent political dissident who has denounced the Thai military's coups in 2006 and 2014, Mr Pavin has also openly criticised King Maha Vajiralongkorn, breaking a taboo in Thailand, where criticising the monarch is illegal.
Mr Pavin accused the army of being behind the attack and said he had been told this by sources. But he said he had no evidence and did not identify the sources or say how they would know.
The suggestion was rejected by Thailand's army chief, General Apirat Kongsompong, who is also head of the king's Royal Guard Force. He told Reuters he had heard about the attack, but was astonished at any idea that the military could be involved.
"I'd say don't be too imaginative. This is not a 'Mission Impossible' movie," Gen Apirat said, adding that a personal dispute might be behind the incident.
"We have our hands full in addressing problems internally in Thailand. And to think that we dispatch people to go assault people overseas - that is impossible," the army chief said.
DISSIDENT FEARS
Mr Pavin said he believed the break-in at his home was part of a trend of attacks on Thai dissidents who have fled the country.
"I think Thai dissidents now have to be more careful, even those living in the so-called First World," Mr Pavin said. "Because even in a safe country like Japan an attack can occur. There is no question that they could attack you any time."
Since December, at least six exiled Thai activists who lived in neighbouring Laos have disappeared.
All of those who disappeared had spoken out against the military and the monarchy.
Criticising the king is punishable by up to 15 years in prison. Fear of prosecution at home was one reason Mr Pavin applied for and was granted asylum in Japan.
King Vajiralongkorn, who was officially crowned in May after the death of his father in 2016, recently swore in a new civilian government headed by former junta chief Prayut Chan-o-cha.
Thailand's government has said it has no knowledge of any of the disappearances of dissidents abroad.
Among the cases that have rattled Thai activists living overseas was that of Chatcharn Buppawan, 56, and Kraidej Luelert, 46, whose handcuffed bodies were pulled from the Mekong river that separates Thailand and Laos in December.
The two men, who helped run an anti-junta radio programme, had disappeared from Laos at the same time as their colleague Surachai Danwattananusorn, 78. Mr Surachai's whereabouts are still unknown.
In February, three other Thai dissidents who had been living in Laos - Siam Theerawut, Kritsana Thapthai and Chucheep Chiwasut - also went missing after they reportedly travelled to Vietnam, and their whereabouts remain unknown.