A serious gambling addiction could have been a factor that pushed Sararat "Aem" Rangsiwuthaporn to murder 14 people using cyanide, police said.

Police said on Thursday that an analysis of the 78 million baht which passed through bank accounts owned by the suspect, who has been dubbed "Aem Cyanide" on social media, suggested she had a gambling habit.

Some of the money was found to have been transferred to proxy accounts which were set up to receive cash transfers from gamblers, police said, noting her supposed victims had transferred large amounts of cash to Ms Sararat's account before their deaths.

An investigation revealed that on one particular day, Ms Sararat lost almost one million baht to gambling.

When asked about the source of the cyanide used to poison the victims, police have a list of 10 possible suppliers.

Police are closing in on one of Ms Sararat's aides who may have been involved in the killings.

Ms Sararat was arrested on April 25 when she was four months pregnant. Her arrest followed a complaint filed by the mother and elder sister of one of the 14 victims.