THE SHOOTING of a security guard as he slumbered in his estate box in Phuket City has police probing a second gun murder mystery in the space of 72 hours.

On Tuesday at 6.10am the body of a young female golf caddy was found crumpled by the roadside near the Mission Hills course in eastern Phuket, killed by a single shot to the back of the neck.

Today the security guard's body, still in a plastic chair, was discovered in metropolitan Phuket City.

Phuket forensic detectives believe the man was blasted with a home-made nine-shot Thai handgun known as a thai pradit.

Prevalence of home-made guns has alarmed authorities because they are considered to be easy to make with a basic technical college education and access to the right equipment.

Petch Security Company guard Winai Buratongkm, 54, was in his chair at the entrance to the Phuket City Municipal Estate in Saphan Hin, Phuket City, when the killer fired through the window sometime overnight.

At least one bullet hit him in the head. The shots zinged over Khun Winai's parked bicycle. Hanging in a plastic holder on the wall was a partly-drunk takeaway container of white tea.

Khun Winai's body was not found until 8am today, by an estate resident who saw the holes in the box window and looked inside. The estate, near the landmark Phuket City incinerator, houses government employees of all kinds.

Phuket City Police Chief Colonel Wanchai Eakpornpit was leading investigations today. He is hoping to interview five teenage boys who were seen talking to the security guard at the box about 9pm last night.

Khun Winai had been working for the security firm for only three months, police were told.

Mission Hills caddy Amornrat Petchtrong, 26, was found lying dead beside her red and black Honda Click about 6.10am on Tuesday. She had been spotted talking to a man earlier. Local villagers discovered her body.