Pimpa Onthong, 20, was apprehended when she took the ill baby to Rasi Salai district hospital in Si Sa Ket yesterday morning. Hospital director Somchai Panumaswiwat alerted police after receiving a tip-off from hospital staff and a neighbour of Pimpa, who reported that she had returned home last week with a baby although she had not been pregnant, investigators said.

Pimpa had already been arrested by Pathum Thani police on Wednesday for using a forged birth certificate to file a birth report in Klong Luang district office.

Pimpa told police that she gave birth to the baby while undergoing an attempted abortion of her seven-month pregnancy. Because the baby was born alive, she reportedly said, she decided to raise it and take it to her mother in Si Sa Ket.

The police in Klong Luang seized the false documents but let her go.

Medical staff at the Rasi Salai hospital became suspicious because of Pimpa's nervousness, her failure to provide information about the baby's birth, the fact that she did not look like she had recently given birth and her refusal to take a physical check-up.

Her appearance resembled pictures of the Lop Buri kidnapper captured on closed-circuit TV at the hospital and aired by the media, Somchai said.

After being questioned, Pimpa claimed that the baby was her sister's, Somchai said. He then took Pimpa's picture and sent it via e-mail to the Lop Buri hospital director, who said it bore a 90-per-cent resemblance to the kidnapping suspect. Somchai called the police.

Colonel Pracha Sripojtham of Rasi Salai police station said Pimpa confessed that she had stolen the baby from Lop Buri hospital on April 14, claiming that she wanted a baby because her own pregnancy had been aborted. Pimpa told police that she was looking for a job at the hospital when she saw the twin's parents, Ratree Trakanchan, 22, and Suprot Khanthongdee, 29, having an argument, so she decided to kidnap the baby.

Earlier, Sakhon Kamto, a 24-year-old woman with whom Suprot reportedly had an affair, had been held by police on suspicion of the kidnapping.

"Pimpa confessed she did it alone, thus Sakhon is believed to have had nothing to do with this case," Pracha said.