Seven charter flights are being used in the operation.
Air China official Zhu Mei said two Boeing 777 aircraft are being used to pick up passengers from Utapao Airport near Pattaya, about 150 km east of Bangkok.
Two passenger planes from China Eastern Airlines and Air China also began their mission earlier on Saturday.
Zhong Ning, a CAAC spokeswoman, said the exact return times of the flights depended on the security situation in Thailand.
"It depends on the organization work of the Chinese embassy in Thailand. The trapped visitors are scattering in Bangkok, and our destination is a military airport, so the embassy should gather the passengers at the airport. I think many Chinese aviation companies have offices there. They will try their best to bring back stranded passengers."
Many foreigners have been stranded in Bangkok after anti-government protesters in Thailand laid siege to the country's main international airport. (WWW.hxen.com)
Among the trapped foreigners are more than 1,000 Chinese nationals, including tourists from the mainland, Hong Kong, Macao and Taiwan.
The first batch of 246 passengers arrived in Shanghai early Sunday morning.