Long-term expat Halpin pleaded guilty to the crime during a court hearing, and because of this, his sentence was reduced to four years and 10 months in prison, a Phuket Provincial Court spokesperson told The Phuket News.
He was fined B500,000, which was later reduced to B250,000 because of his confession.
Halpin was arrested on December 14, 2013. Phuket Police said they first caught a man named Loesak, also known as Nan Thaitae, 25, in possession of ya ice, around 9.30pm on December 14. He told police that Halpin had bought ya ice from him, with the intention of selling it to tourists and teenagers in Chalong, Karon, Rawai and other areas.
Police asked Loesak to call Halpin to set up a deal, then swooped on the New Zealander at the Chalong Villa Resort and Spa.
In the room where Mr Halpin was staying, police found 18.45 grammes of ya ice, a digital scale, a Samsung Galaxy phone and other drug-related equipment, including a makeshift pipe for smoking ice.
Halpin was arrested and charged with possession of a category one drug with intent to sell. Initially he admitted possession of the drugs but denied he was selling.
At the time of his arrest, Halpin, 52, was a former long-time Tourist Police Volunteer, and very well known across the island – particularly in Chalong where he lived and was based for work.
Halpin used to own a dive shop called Raya Divers on the Chalong Pier road, with another shop in Khao Lak, but it is not known if he was still involved in the running of the business.
Halpin was understood to have lived in Phuket for at least 15 years and has a 13-year-old daughter who lives on the island.