Thai authorities have been accused of fabricating evidence in some past cases but netizens were split over the latest fakery, some condemning the manipulation of the image while others wished it was real.

Widespread flooding has hit southern Thailand in recent days, with the government confirming that at least 55 people have been killed so far.

The 437th Border Patrol Police unit published the image of gun-toting rescuers on its Facebook page after social media footage recorded sounds of shots being fired as volunteers on jetskis worked in a flooded neighbourhood in Hat Yai neighbourhood.

"Border patrol ready to enter zone 8 today," read the caption, along with a laughing emoji.

However, AFP factcheckers using Google's AI identification tool SynthID found digital watermarks in the image.

A star-shaped Gemini watermark was also visible in one corner, indicating that the image was created using Google's AI software.

The police unit apologised on Thursday and published the original picture, which showed unarmed officers in a boat wearing orange lifevests rather than helmets and body armour.

Rescue supplies are visible in both versions.

"This is a real image before it was made into an AI image," it said. "We apologise for any misunderstanding."

No one has been punished over the incident, the border police unit told AFP on Friday.

"We generated the photo just to show the public our readiness to enter the area," an officer told AFP, declining to give his name.

None of its personnel working on flood relief carried firearms, he said.

The manipulated post came despite Thailand's government-run anti-fake news centre issuing a warning on Facebook beforehand that said: "Don't share AI images that mislead people and becoming obstacles to relief efforts."

Netizens criticised the use of AI. "Don't do this again, you must understand the importance of communications during a crisis," one said.

Others urged authorities to make it a reality, with one saying: "From the heart of a local in Hat Yai -- this is what people want."