Former soldier and para-athlete Chaturong Suksuk took the life of his wife Kanchana Pachunthuek, a few hours after they had crowned their love.
According to local media reports, the guests noticed that the groom did not look happy at the party. He suddenly left the wedding and returned with a gun.
First, he shot dead the bride's mother and younger sister, along with another person invited to the wedding, while one guest was seriously injured.
Officers told the Bangkok Post that eleven bullets were found at the scene of the shooting, in Wang Nam Khieo district.
29-year-old Chaturong had served in the army, from which he returned injured after one of his legs was hit by a train and doctors had to amputate him.
He won a silver medal in swimming at the Asean Para Games in Indonesia last year as a para-athlete and was on the list of athletes competing at the World Skill Sports Games in Thailand next month.
But Chaturong seems to have felt insecure about the 15-year age gap between him and his wife. Police told the BBC that this remains speculation, but what is certain is that Chaturong "was quite drunk when he committed the crime" and his motive remains unclear.
(A2 Televizion)