Chularat Thowanna’s body was found on her bed on Saturday.
A knife was found at the scene of the crime.
Police said her boyfriend, a police officer in Nakhon Pathom’s Sam Phran district, tried to call her but her phone was not on.
He asked Chularat’s teacher friend who lives nearby to check on her.
The teacher friend broke into the locked room and found her body.
Chularat’s phone and a gold necklace were missing.
Police arrested Chatri Ruamsoongnern, 27, a cement factory worker who rented a room in the same apartment building as Chularat.
Chatri reportedly went to work after allegedly committing the crime, and authorities apprehended him when he returned to his apartment.
Police found that Chatri had scratches on his back and chest. His left hand also had a deep wound.
Authorities plan to bring him to re-enact the crime at the rented room.
Chatri said he had been a secret admirer of Chularat and learnt that she did not lock her room because the knob on the door was broken.
Police said Chatri was released from jail last year after being convicted of rape in 2013.
Police released two Cambodian workers after discovering they had no part in the crime.
Sanit Thowanna, 59, Chularat’s father, said his wife could not come to the police station, as she could not accept the loss of their daughter.
Villagers turned up at Kaeng Khoi Police Station holding |placards with messages calling for Chatri to be given the death sentence.