Belgian Ferdinand Salpdew, 62, dripped a trail of blood through their Patong apartment block as his distraught lover, upset at what she'd done, escorted him for treatment.
Bruised and angry, Yossapa Janthep, 36, wielded a sharpened steel rod and struck Mr Salpdew five times in the chest, once in the throat and once in a leg.
When the pair arrived at Patong Hospital, Yossapa was still grasping the weapon. Mr Salpdew remains in a serious condition today at Bangkok Hospital Phuket in Phuket City after being transferred from Patong.
A sordid story of jealousy and rage emerged as police and paramedics asked what had happened.
They were told that Mr Salpdew and Yossapa had been together for six years but he'd only just returned to Thailand after a time away.
To celebrate they had dinner at a hotel then went out to enjoy the bars of Soi Bangla. Mr Salpdew contacted a Belgian friend and when they met up, Yossapa began paying a lot of attention to the younger, good-looking man.
After a time, Mr Salpdew grew so jealous that he took Yossapa back to their apartment where he beat her for looking at the other man.
In anger and pain, police said, and quite drunk, Yossapa lashed out at Mr Salpdew with the weapon.
It's not clear at this stage whether Mr Salpdew wishes to press charges.