"There were no signs of struggle and his belongings seemed to be in order. We also found a lot of prescription medicines in the room."
Police believe the man may have died from a pre-existing medical condition.
The man's body was taken to Vachira Hospital in Phuket Town. The Phuket News reported police had notified both the British and New Zealand embassies, but were still waiting for confirmation that the man's family has been notified of the death.
The Phuket News did not name the man.
A spokeswoman for the Ministry of Foreign Affairs and Trade said the ministry was aware of media reports of the death of a dual national in Phuket and confirmed the New Zealand Embassy in Bangkok had been notified of the death.
"For privacy reasons, we are unable to comment further on this case," the spokeswoman said.