Mr Zhang was speaking after visiting the detainees at the immigration office in Sadao district.
He said Chinese authorities had verified that they are Muslim Uighurs from northwestern China.
Chinese authorities even know their home addresses and the names of their parents, he added.
The information obtained by Chinese officials has confirmed the migrants were smuggled in by a human trafficking gang involving both Chinese and Thai nationals, Mr Zhang said.
He said investigations are under way to find those behind the smuggling of the Muslim Uighurs.
Songkhla immigration office chief Pol Maj Gen Thatchai Pitaneelabutr said Thailand was still trying to verify the nationalities of the remaining migrants as quickly as possible.
The illegal migrants, arrested early this month in Songkhla's Sadao district, are thought to have fled China's restive Xinjiang province for Kunming province before entering Thailand via one of four human trafficking routes. It is thought their end destination was Turkey via Malaysia.
They were arrested at a rubber plantation on March 12 and claimed to have arrived via Turkey.