Prasittichai Khaokaew, 38, former director of a primary school in Sing Buri province, was taken to the court, on Ratchadapisek Road in Bangkok, to hear the judgement.
Public prosecutors arraigned him on nine counts, including three murders and attempted murder.
The court was presented with evidence that Prasittichai was armed with a pistol fitted with a long sound suppressor when he robbed a gold shop shop inside Robinson shopping mall in Lop Buri on Jan 9.
He killed Theerachat Nimma, a security guard at the mall, two-year-old Panuwit Wongyoo and Thidarat Thongthip, a woman employee of the gold shop.
He also shot and seriously wounded a fourth person before fleeing on a motorcycle with 33 gold necklaces worth about B665,470. He was later caught and confessed to all charges.
The court found him guilty on all counts and sentenced him to death, with a fine of B1,000, and ordered him to pay compensation to the families of all victims, plus interest at 7.5% per year.
The callous murder and robbery occurred at Aurora gold shop inside Robinson shopping mall on Phahol Yothin Highway in tambon Kok Ko of Lop Buri’s Muang district about 8.44pm on Jan 9.
Surveillance camera footage showed the robber shooting with a pistol at customers and gold shop staff as he walked up to the store counter.
He fired without hesitation at a two-year-old boy walking past the shop with his mother. The robber shot dead a security guard as he left.
After a weeks-long manhunt, police investigators finally arrested Prassitichai. Some of the loot was found hidden in his father’s carport roof.
He had posted pictures on his Facebook page of himself and his wife, also a school teacher, taking a child to a milk shop on Jan 11, two days after he robbed the gold shop. It was Children’s Day.