Army chief Apirat Kongsompong has vowed to end unsound army projects, after these were raised as a possible motive behind a soldier's shooting spree in Nakhon Ratchasima that left 30 dead and 58 wounded.

Speaking at the Royal Thai Army headquarters on Tuesday, Gen Apirat apologised for Jakrapanth Thomma's rampage in a Korat shopping mall on Saturday.

"The moment he pulled the trigger he became a criminal, not a soldier anymore," he said.

The army chief admitted the shooter was maltreated by his commanding officer and the officer's relatives, and admitted there were many "unsound" projects, including for welfare housing, loans, and projects which involved cooperation between military units and merchants.

Gen Apirat said he had already terminated some of these projects, adding this was the first step in sorting out problems that had plagued the army for a long time.

He said that he had opened a channel via which lower ranks could file complaints against their superiors directly to him.

"As commander of the army, I apologise and I am wholeheartedly sorry that the man behind the incident was a soldier," he said, referring to 32-year-old Jakrapanth.

"I extend my condolences to the relatives of the slain victims."

Twenty-nine people were killed, and 58 other people suffered wounds before the gunman was killed by police commandos.

Apirat failed to hold back tears as he mentioned the people killed during the rampage.

"There are people who criticise the army. I urge them not to blame the army ... because the army is a sacred organisation ... Blame me", he said.

The army chief said he had no intention of resigning from his post. He is due to retire in September.