Praewa Rinchalee was admitted to Kasemrat Hospital at about noon on Wednesday with a cracked skull and bleeding in the brain. She died yesterday.

Ratchadaporn, 33, left her baby sleeping alone on the fourth floor of their home in Ramkhamhaeng while she went downstairs. The door to the balcony was still open.

Ratchadaporn said she heard her baby scream so she ran upstairs and found the girl was not in bed.

She rushed out to the balcony where she looked down and saw her baby lying motionless on the ground.

She said her daughter might have crept out on the balcony to look for her after she woke up and then slipped through the bars.

Police plan to summon the mother for questioning after the baby's funeral.

Dr Surapee Ruangsuwan, director of the Queen Sirikit National Institute of Child Health, warned parents never to leave their babies alone even while the infants were sleeping, especially those who were already old enough - at eight or ninth months - to start crawling around.

"Parents should close windows and doors or barricade the balcony to prevent such accidents," she said.