Nakhon Ratchasima acting zoo director Narongwit Chodchoy said it was a good omen for Chinese New Year and Valentine's Day.
He said it was the first time in Asia that the vulture had laid an egg in her cage.
The working team of the Condor Population Rehabilitation Project in Thailand has been waiting all year round.
The Asian king vulture is protected wildlife and only five are left in the country.