A rogue soldier who killed 29 people in an overnight shooting rampage in Thailand was shot dead yesterday morning, as Prime Minister Prayut Chan-o-cha acknowledged that the army may need to address mental health issues within its ranks.

"We need to look into mental health issues," he told reporters in Nakhon Ratchasima province after visiting the victims yesterday, when asked if mental health was linked to the tragedy.

"I used to be an army commander, so I know. Those colonels, captains, my subordinates had this problem. You have to get closer to them to identify it. But sometimes, they don't tell, like in this incident."

Mass shootings are rare in Thailand outside of the restive south and the more than 14-hour stand-off at Terminal 21, a popular mall in downtown Nakhon Ratchasima packed with weekend shoppers, left security officials scrambling to evacuate hundreds of people while urging those trapped inside to hide for their safety.

The province is a four-hour drive from Bangkok.

Earlier on Saturday, Jakrapanth Thomma, a 32-year-old sergeant-major, shot three people, including his commanding officer, inside Suratham Phithak military camp, seized three machine guns and more than 700 rounds of ammunition from the barracks, and drove to the shopping mall about 20 minutes away in an army vehicle.

According to Mr Prayut, the initial killing was related to a dispute over land sales commission.

On Saturday, the suspect had posted on Facebook: "Being rich by cheating and taking advantage of others. Do they think they can bring that money to spend in hell?"

He proceeded to post updates of his shooting spree on Facebook until the social media giant removed his account on Saturday.

Terrified mall-goers rescued early yesterday described the unnerving hours they spent in hiding as the gunman prowled the mall.

Ms Samorn Chumkratok, who had earlier gone to the mall to exercise, hid in the restroom.

"I was terrified in the restroom, just praying and asking my parents' spirits to protect me," she told Nation TV channel.

"I didn't move and waited for officials to advise. They called me on my mobile phone and asked me to stay quiet."

Ten-year-old Apinan Dingklang, meanwhile, was taking a science tuition class at the mall when he heard what he thought was the sound of firecrackers. He was later taken to a gym and stayed in its restroom.

"My mother kept calling me on my phone. She told me to recite Buddhist verses and stay put," he told Nation TV.

As the impasse dragged on, Thailand's national broadcasting regulator demanded late on Saturday that news outlets stop broadcasting rescue operations live, for fear of giving the gunman clues of the authorities' plans.

Police also picked up the suspect's mother from neighbouring Chaiyaphum province, to try to get him to surrender.

He was eventually killed inside the mall yesterday morning.

When it was all over, the facade of Terminal 21 was marked with bullet holes and spent shell casings littered the floor.

Prime Minister Prayut defended the security officers' professionalism. "It was not that we are not capable but we needed to be very careful," he said.

"The building covers six floors and there were many people inside, so it was not easy," he added.

"Our officials are experienced and well trained but this is the first time it happened in Thailand. We hope it will never happen again."