Col Chanapat Nawalak, chief of Nong Kham police, identified the Chinese tourist as Gao Li Ping, about 35. She was wearing a white T-shirt, red shorts and a white wide-brimmed hat at the time of her disappearance.
Mrs Gao was reported to have last been seen about 6pm on Sunday while touring the zoo.
About 100 police and search and rescue staff of a local charity foundation began scouring the zoo in steady rain to find her.
The search was called off on Sunday night without any trace of her being found.
A Chinese tour guide told police Mrs Gao travelled to Thailand after breaking up with her husband. She appeared to be under stress and often separated from the tour group to be alone.
Col Chanapat said the search resumed yesterday morning and footage from the 122 security cameras installed around the zoo was being examined in the hope of locating her.
By late yesterday afternoon there were still no reports her being found.
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