Police responded to a domestic violence call at 4.30pm and dispatched officers to a 2-storey townhouse in Sisunthon.
At the scene they met a group of residents surrounding 56-year-old Mr Wira Bunnaruck, whose face was bloodied up from open wounds on either side of both eyebrows.
Rescue workers treated the wounds before transporting the man to Thalang hospital.
In the house, police met the aggressor Mr Trirong Detpongha, who had been waiting to be arrested.
Mr Trirong told police that he had used a brick to attack his step-dad, Mr Wira, who was yelling at and beating his mother.
Police soon learned that Mr Trirong was already wanted on a warrant in Chalong for statutory rape, in other words, engaging in sexual activities with a minor – a girl younger than 15, the legal age of consent in Thailand.