The Chiang Rai Times newspaper said Brian Lee was yesterday taken into police custody after forensic evidence and footage from a security camera showed he had allegedly lied about a fight he claimed occurred between his wife and mother - which ultimately led to her death.
He told police his mother, who suffered from dementia, became angry at his wife and, as a result, grabbed her and slammed her head against a wall.
His wife then apparently stabbed the elderly woman in retaliation, Lee told police.
When authorities took Lee's wife away, she appeared stressed and had threatened to harm herself.
Local media also ran photographs of Lee on that day; showing him presenting two letters to police.
He said his wife had written both - one written before and after the incident - describing the rocky relationship between the two women.
However, after studying the forensic evidence and security camera footage, police concluded that Lee was lying about the quarrel and took part in the killing of his mother.
His wife Park Songhee is presently under police watch at Chiang Mai Hospital.
Police said Lee's mother had several apartments and businesses in South Korea, and Lee had brought her to live with them in Chiang Mai six months ago.
A Ministry of Foreign Affairs and Trade spokesman said the New Zealand Embassy in Bangkok was in contact with local authorities regarding the situation.
No further information would be provided, for privacy reasons, he said.
