Jealousy was the motive for the gruesome murder of the Japanese teacher who was the new husband of the Thai wife, the Court ruled.
But both confessed to their crimes against Mr Yoshinori Shimato and had the death sentence commuted to life term for the Thai husband, and his wife 20 years.
Somchai Keawbangyang, 47, and wife Pornchanok Chaiyapa, 47, were charged with the murder of Mr Shimato, the new husband of Mrs Pornchanok, and chopping his body and throwing the pieces into a canal in Bang Bo district of Samut Prakarn in September 2014.
Both are still facing another murder case in which a Japanese businessman died 11 years ago.
In the case in 2003 a Japanese businessman Kisitoshi Tanaka died falling from the third floor stairways of an apartment room in Bang Plee, Samut Prakarn where he rented and lived with his Thai wife Pornchanok.
In this case, the death was recorded to be accident and insurance payment had been claimed by Mrs Pornchanok
But suspicion arose when the Thai couple were arrested for murder of another Japanese teacher in 2014, 11 years later after Tanaka’s death.
Intense interrogation by the police over Tanaka’s death in 2003, forced Somchai to admit to killing the Japanese businessman out if jealousy.
He admitted to push the Japanese husband of his wife down from the stairways outside the victim’s third floor room.
He recalled that he had a drink before with the victim but left the room later.
However he returned again and called up Mr Tanaka to open the door. When Tanaka came out, he assaulted and pushed him down the stairways.
Tanaka fell on the stairways of the second floor unconsciously, he said adding that he pulled up his head and pressed his neck in between the stair grill and stepped on his head with his leg until he died.
He said he killed the Japanese businessman as he was jealous with him getting married to his wife.
Somchai affirmed that in this murder he did by himself with his former wife Pornchanok knowing nothing about it.
Earlier information revealed by Tanaka’s daughter Ms Keiko Matta aroused the police to look into the possibility of another murder case rather than normal accident.
She said earlier before her father’s death, Mrs Pornchanok bought insurance policy for his father, and after his death was quick to claim the insurance money for herself.