Dated May 2, the letter was purportedly sent by Ambassador Sarun Charoensuwan to Cha Myung-seok of the May 18 Memorial Foundation.

The letter began being circulated on Thai social media on Monday.

Pai Dao Din, real name Jatupat Boonbattararaksa, was awarded the foundation’s Gwangju Prize for human rights.

In the letter, the ambassador said the activist had violated lese majeste and computer crime laws and had his bail revoked in December.

The ambassador said Pai was receiving a fair trial.

He emphasised Thailand gave importance to freedom of expression but within reason to maintain order.

The Thai Embassy in Seoul could not be reached for confirmation of the letter’s authenticity.

On Monday, the Khon Kaen Court jected Pai’s bail application.

As a result, he will not be able to collect the prize in person at a ceremony in South Korea next week.

He was awarded it for his courage in fighting against a non-democratic regime, according to the foundation.

Pai has been imprisoned for almost half a year after sharing on Facebook a BBC article deemed to have insulted the monarchy.