I don&;t remember going back to Zhuhai at Baiyun Airport. Anyway, there is no need to leave the airport. There is a ticket office directly in the airport where you can buy tickets. From Zhuhai to Baiyun Airport, I know there are two airport lounges: one is next to Starbucks in Gongbei Zhongzhu Building; One is next to Huazi Shidong Station. There are airport buses to Baiyun Airport in both terminals, so it is recommended to buy air tickets in advance to avoid missing the plane.