The father of a woman who died of poisoning in Thailand has described how his last words to her were that she was a strong girl and that he loved her.

Richard Carter said his daughter Sarah, 23, was too ill to reply and he did not realise then that she would not make it.

"She couldn't speak back because she had tubes in her mouth, but we never thought it would come to this. I just told her she was a strong girl, with a strong mind and that she could get through. I told her that I loved her."

Mr Carter said his daughter was excitable, friendly, unbelievably loving and always put others before herself.

"All she did was think of other people ... even before she left, all she could think of was the presents she was going to get us.

"Then her mother, Anna, found her diary in her hotel room and there was just a huge list of things she wanted to get us. But she only managed to get a few and was never able to get them all."

Authorities in Thailand are still investigating what poison killed Miss Carter and left two others seriously ill.

Amanda Eliason and Emma Langlands are still recovering in Chiang Mai Ram Hospital.

"They all left on their trip and we just saw them off with best wishes. We never expected this to happen," Mr Carter told the Herald.

Bunches of flowers, gifts of food and cards from loved ones fill Mr Carter's house as he waits for his son and wife to bring home the body of his eldest daughter tomorrow.

When the three young women got sick they did not realise how ill they were - it was only after a hotel staff member found them that they were taken to the hospital, Mr Carter said.

"So they got to the hospital and were on the mend. We had a talk to Sarah and she was good ...

"Apparently within an hour it sprung from their stomachs into their hearts and that's where the trouble started.

"We were just shaking in the kitchen listening to the call. Anna [her mother] knew more than I did because she's a registered nurse. I was thinking, 'it can't be too bad because it's only food poisoning'. But Anna immediately realised she needed to get on that plane."

While his wife was in transit late on Saturday night he kept checking with the hospital on Sarah's condition, he said. "Then suddenly I got the dreaded call that I didn't want to hear ... I had the horrible task of calling Anna at Bangkok Airport. It floored her.

"She then had to fly to Chiang Mai. Not to meet up with Sarah, but to collect her things."

It was first reported that the group had eaten toxic seaweed as part of a meal they had bought at a Chiang Mai food market. However authorities say there were no traces of seaweed in Miss Carter's system.

Dr Winai Wananukul, of the Poisons Centre in Bangkok, said: "There was no history of [seaweed] ingestion in our record. The seaweed was also not in a list of foods [she had eaten] days before." The case was being investigated by the provincial healthcare team, he said.

Miss Langlands, who was the least affected, has since moved into a general ward. Miss Eliason was still in the intensive care unit yesterday, but was said to be recovering well.

- Additional reporting Vaimoana Tapaleao, NZPA