Police want to question an actress who bought cyanide from the same batch as that of suspected serial killer Sararat "Aem" Rangsiwuthaporn.

The actress, whose name was withheld, was found on a list of 100 buyers who purchased from the same batch as Ms Sararat.

Police may summon the actress next Monday or Tuesday to question what she needed cyanide for, police said.

Police will also expand their investigation into whether the sale of the batch of cyanide was illegal and will check if Industrial Works Department officials were involved with any illegal sales.

Meanwhile, Ms Sararat's ex-husband, Pol Lt Col Withoon Rangsiwuthaporn, will be released on bail with a surety of 100,000 baht and must wear an electronic monitoring bracelet.

The court said that up until now, no evidence confirmed his association with any alleged murders.

Police said that all of Ms Sararat's 15 alleged victims -- 14 of whom died and one who survived -- had been poisoned.

Money was the main motive for the alleged killings, police said, adding that Aem had poisoned all 15 victims with cyanide placed in drinking water, food or medicines. She had huge debts from credit cards.