Most of the victims were at the city's Terminal 21 shopping center, where the shooter held out against an overnight siege with an assault rifle and ammunition stolen from his army base.
Police named him as 32-year-old soldier Jakrapanth Thomma. He initially posted written messages on Facebook during the attack before his account was shut down by the company.
"It was a personal conflict...over a house deal," Prime Minister Prayuth Chan-ocha told reporters on Sunday from Nakhon Ratchasima after traveling there to meet wounded survivors.
Prayuth added that the conflict was with a relative of the soldier's commanding officer.
