She saw her baby murdered on Facebook Live

PIC: A memorial photograph of slain 11-month old girl Natalie is displayed at a temple in Phuket on Thursday. (AFP)

The distraught Thai mother of a baby girl killed by her boyfriend in a murder he broadcast on Facebook Live has described the harrowing moment she stumbled across the video and rushed to alert police.

The killing on Monday evening caused revulsion both in Thailand and around the world, sparking renewed debate about what can be done by social media giants to more quickly remove live broadcasts of violent crimes, suicides and murders.

Jiranuch Trirat, a 22-year-old from Phuket, was left devastated after her boyfriend Wuttisan Wongtalay hung their 11-month old daughter Natalie from the side of an abandoned building before taking his own life.

He broadcast Natalie's murder on Facebook Live, a video that Jiranuch came across that evening.

"I was with my older brother and he was logging onto his Facebook," she told AFP on Thursday from a Phuket temple where daily prayers were being held for Natalie ahead of her cremation on Saturday.

"He was scrolling down and suddenly we saw the live broadcast. I turned to take a look and saw him (Wuttisan) drop my daughter with the rope and I couldn't continue to watch."

Jiranuch Trirat stands in front of the coffin of her slain 11-month-old daughter Natalie at a temple in Phuket, Thailand. (AFP)

The horrifying realisation of what was unfolding sparked a desperate search by relatives and police, with the bodies of Wuttisan and Natalie found just a few hours later.

The murder video remained on Facebook for around 24 hours, prompting cries for the social network to move more swiftly to take down clips of grisly crimes and killings.

But Jiranuch said she harboured no ill will towards Facebook, stating the social network had little initial control over what users choose to upload.

"I don't blame Facebook. They are not part of the problem, we can choose to broadcast happiness or sadness," she said.

What prompted Wuttisan to take such a horrifying step remains a mystery.

Jiranuch said the two frequently argued, particularly over her ex-husband with whom she has a son nicknamed Sanook -- the Thai word for fun.

"He often abused my son Sanook," she said.

But Wuttisan had always been kind to their daughter Natalie, she added, looking after her in the day while she took classes at a nearby school.

As for what her boyfriend did, Jiranuch said: "I forgive him because holding onto anger for a long time will not get my daughter back."