Thai Airways International president Sumeth Damrongchaitham has reminded staff of the national airline's political impartiality in the wake of online selfies posted by flight attendants posing with Future Forward Party leader Thanathorn Juangroonruangkit.

Mr Sumeth issued the caution in a video clip to employees distributed on the national airline's internal network on Wednesday.

It was in response to selfies posted online by flight attendants travelling on an aircraft with Mr Thanathorn. The pictures drew criticism and sparked argument after they were posted.

"Our company is a state enterprise. We are an organisation that is neutral in all matters. Staff of Thai Airways International represent the organisation. Whenever you are in uniform, show our logo or are in our places, please keep in mind that all your actions represent the organisation," Mr Sumeth said.

He said staff must to be careful about work-related photographs and messages communicated through social media.

"What we do sincerely, without any agenda, may be used [by others] as a tool to start a trend or damage the image of the organisation," Mr Sumeth warned.