Second Army Region commander Tharakorn Thamwinthorn believes Khon Kaen deputy governor Suchai Butsara may be the victim of an unlucky accident or a deliberate set-up as a letter reportedly signed by the official causes controversy ahead of a visit to the province by Prime Minister Prayut Chan-o-cha.

The letter, issued by City Hall on March 9, calls for provincial authorities to work on a mission to "end people's stupidity" as they prepare for the PM's upcoming cabinet meeting and tour of Khon Kaen.

It was signed by Mr Suchai, acting on behalf of the provincial governor, and was meant to be delivered to the president of the Khon Kaen Provincial Administration Organisation (PAO).

In the letter, City Hall assigned the PAO's promotional office, provincial education officers and the public health office to work on a mission to "make people end their stupidity." Officials were also asked to meet at City Hall on March 13 to figure out how to do this.

The letter, which has been widely shared on social media, has sparked criticism from netizens as well as local people in Khon Kaen.

Lt Gen Tharakorn said on Sunday he would contact Mr Suchai and ask him to explain the incident. It remains unknown whether the wording used in the letter was a technical error, a deliberate attempt to smear the acting governor's name or a form of contempt.

An inquiry is needed to find out who drafted, printed and reviewed the document, he said.

"I believe someone may have framed the deputy governor. The drafter, printer or reviewer should have known that using the word ngo (stupidity) was not appropriate, and the letter should not have been brought to the deputy governor for signing," said Lt Gen Tharakorn.

Meanwhile, Mr Suchai has conceded the letter is legitimate and not a forgery. He said he issued a follow-up letter on March 12 that amended the wording used in the first version.

"I have to offer my apologies to the public as they may have been confused by this," said Mr Suchai.

He said he received the letter from the PAO and signed it right away on March 9. He did not check it thoroughly as the letter merely called for a second meeting at the province's City Hall and he was pressed for time.

"Afterwards, some people complained that the letter contained improper wording, so I quickly fixed it and issued a new letter to be sent out to various agencies," said Mr Suchai.

He insisted the amendment had been made before the controversial letter was shared online.

Mr Suchai said the governor has ordered a panel to look into the incident.

Pornthip Khamchuen, chief of the Local Administration Promotion Office in Khon Kaen, admitted to writing the original letter on Sunday and apologised for the inappropriate wording that was used.

The Interior Ministry has also apologised to the public.