Ms Carter and two travelling companions became ill on February 3 after staying at the hotel.
Her friends recovered but she died in hospital three days later of myocarditis - acute heart inflammation.
On February 2 a Thai woman died after becoming sick while staying in a room next door to the New Zealanders. An elderly British couple died in the hotel on February 19 of apparent heart failure.
Two other tourists died after falling ill in the city in January, and Thai authorities made a six-month investigation to establish the cause of the six deaths.
The Downtown Inn, owned by a former mayor of Chiang Mai, remained open during the investigation.
The final report did not draw direct links between any of the deaths except Ms Carter and the Thai woman next door.
The closest the report got to an explanation was to say Ms Carter's death "can be explained by exposure to some chemicals such as those found in pesticides".
It did not identify any specific agents involved or how the poisoning may have occurred.
Mr Carter said his daughter's friends had arranged for a park bench to be erected in her honour at Macleans Reserve, East Auckland, and a tree had been planted at Macleans College in remembrance.