A Frenchman in Thailand who posted a Facebook video clip making fun of a song composed by Prime Minister Prayut Chan-o-cha says he has apologised to the junta in writing.

Yan Marchal posted the apology on his Facebook at 5pm on Wednesday.

The clip, which had already been removed from his Facebook, showed him singing in Thai Returning Happiness to the People, a song composed by Gen Prayut with modified lyrics against the familiar NCPO backdrop during the TV programme of the same name hosted by Gen Prayut on Fridays over the past five years.

After the clip was uploaded, Mr Marchal claimed it drew 1 million views in 24 hours and he received a thousand friend requests. But his joy was short-lived.

In the post on Wednesday evening, he wrote two policemen came to his house to ask him to sign a memorandum admitting that making the clip was an improper act and that he was sorry and would not do it again.

The signed document, which was shown on his Facebook by the request of his visitors, also stated he had acted alone and that he "would like to say sorry to the government and the people of Thailand on my improper behaviour which causing the damage against the National Council for Peace and Order (NCPO) and the people of Thailand".

The document also said he agreed to make another clip apologising for his actions to the people of Thailand.

Mr Marchal said he was planning to take a break from posting about politics. "That clip made many more people laugh than it made people angry, but still, it made a few people angry, and I derive no pleasure from that," he wrote.