In his first detailed press conference since the horrific weekend mass shooting where a rogue soldier killed 29 people and injured 58 others, an emotional Thai army chief Apirat Kongsompong apologised yesterday for the tragedy and vowed to reform the military.

He also promised to take care of the victims and their families, and even provide unconditional employment for their children.

"The perpetrator was in our armed forces. I apologise to the people and officials injured in this operation," he said.

But Gen Apirat made clear he would not resign. "I take responsibility for whatever I order my subordinates to do. But I can't take responsibility for an individual's crime."

He said the rogue soldier, Sergeant-Major Jakrapanth Thomma, 32, was upset that he was denied a pre-agreed commission over a land purchase that involved a senior officer and his relative.

Using personal weapons bought under an army welfare scheme, Jakrapanth killed both of them on Saturday. "The moment he shot and killed, he was a criminal, no longer a soldier," said Gen Apirat.

At a military camp in Nakhon Ratchasima, Jakrapanth used a high-powered gun to break the lock of the armoury and then rammed the door with a stolen army jeep. He made off with automatic weapons and over 700 rounds of ammunition that he used for the carnage later at Terminal 21 shopping mall, some 20 minutes drive away.

Jakrapanth also posted updates of his shooting spree on Facebook before he was shot dead.

"We are not lax in security measures. Any units which are lax will be punished. But in this case, (Jakrapanth) worked in that unit, so he knew what to destroy and where to take what he wanted," said Gen Apirat.

"We admit that not all units may be up to standard. That depends on each commander. If any units need to be improved, we will certainly do it."

Thailand's powerful army is a key player in Thai politics, having staged at least a dozen coups since the end of absolute monarchy in 1932.

Former army chief and coup leader Prayut Chan-o-cha has been Prime Minister since the last coup in 2014. Of late, the army has come under heavy scrutiny for its large budget and business interests that include television and radio stations.

After the weekend's unprecedented mass shooting, the public unleashed its anger and dismay at the army, with the hashtag #ReformArmy still trending on Twitter yesterday afternoon.

"Don't scold the army, don't scold soldiers. The army is the security entity and it is a sacred entity," said Gen Apirat.

"Come scold and blame me because I am the army commander."

He promised to make swift changes, including introducing a direct channel for junior soldiers to report on the wrongdoings of their seniors. All information submitted will be sent directly to him, he said.

"The most important thing is our subordinates. We have to take very good care of our soldiers, down to the privates, and especially (those in the lower ranks)," he said.

Commanders who fail to do so will be sacked, added the army chief. "We need to get rid of them, at every level."

Those who are found abusing the army's generous welfare privileges or cheating their colleagues will also be punished, he warned.

The army, for example, provides free housing for its charges, but some retired officers continue to live in army-provided accommodation.

Meanwhile, any soldier who wants to buy personal guns under the army's welfare scheme from now on will need to be approved by a general, instead of a major.

"The perpetrator owned five guns bought under the welfare scheme," Gen Apirat said grimly. "Soldiers don't need personal guns. We have state-issued guns."