Thai police have arrested the wife of a senior officer on suspicion of murdering nine people by poisoning them with cyanide, officials said Wednesday.

The woman, aged in her 30s, was arrested in Bangkok on Tuesday over the killings, which took place over several years.

Investigators believe money was the motive in the killings, Royal Thai Police spokesperson Archayon Kraithong told AFP.

Surachate Hakparn, the deputy national police chief told reporters that a 10th victim had survived after vomiting.

"The suspect went to have dinner with (a woman), who threw up but survived. She is also the wife of a policeman," Surachate said.

Police said the woman denies all the allegations against her.

"The autopsy has found out that there is cyanide in the bodies," Surachate told reporters.

"So it means that the victims have taken the poison by mouth."

Police initially suspected the woman of murdering her friend in Ratchaburi province, west of Bangkok, about two weeks ago.

Local media said the victim collapsed on the bank of the Mae Klong River after releasing fish as part of a Buddhist ritual.

After questioning the suspect, investigators linked her to other cyanide poisoning cases in Kanchanaburi and Nakhon Pathom provinces.