Is it possible to online book bus-tickets to Baiyun Airport from Macau? If yes, How?

Well, there is no direct bus to CAN from Macau. You may get to Border Gate and enter Zhuhai first.
Then take the bullet train from Zhuhai Railway Station and get to GZ South Railway Station.
After arriving, take subway line 2 to Jiahewanggang Station and transfer to line 3 to the destination.

The online booking website only has Chinese version. As I know, TravelChinaGuide provides train tickets online booking service. You can ask help for them. If interested, their contact information is bookingtravelchinaguide.com. In addition, just purchase the subway tickets when you arriving there.

Thanks for the response.
Would be glad if you can guide to book 'online Bus tickets' from Gongbei to GZ Airport Shuttle.