Two online pranksters who boasted they would copy Saturday's mass shooting at Korat's Terminal 21 were arrested on Monday.

Peerapat Chusang, 27, from Chaiyaphum province on Monday turned himself in after a threat he made on Facebook was shared over 10,000 times in a single day.

On Sunday night, on a Facebook page under the name of "Hia Arm Motor", he hinted he would carry out a mass shooting at the Robinson Department Store in the Northeast province of Chaiyaphum.

"Terminal 21 Korat ... I will go to Robinson Chaiyaphum. A downtrodden dog has no gratitude," he wrote. The post also featured images of a gun and of Mr Peerapat wearing the uniform of a high-ranking soldier.

Mr Peerapat told police that he worked at a motorcycle shop in the province and said he had never meant to harm anyone.

He admitted to being drunk and arguing with his girlfriend just before posting the threat on Facebook, adding he had downloaded the image of the gun from the internet. He said he had once served as an army private in Nakhon Ratchasima (also known as Korat), and the uniform he wore in the picture had belonged to his superior.

Mr Peerapat was fired by his boss for showing disrespect to the families of victims killed in the mass shooting on Saturday.

Meanwhile, police also arrested a 16-year-old boy in Roi Et province after he used social media to threaten a mass shooting at a local Big C Superstore.

"After Korat ... the next stop is Roi Et. A downtrodden dog like me will do it," he wrote. He also posted a photo of himself dressed in army-style camouflage pants.

The boy told police he posted the threat just to entertain himself.

The online pranks followed what is being called the most horrific mass shooting in Thai history. Perpetrator Jakrapanth, 32, had served as a soldier in Nakhon Ratchasima province before he killed 29 people and injured 57 on Saturday.

Pranksters could face a jail term of up to five years and/or fine of up to 100,000 baht under the Computer Crime Act.