How to get from Baiyun Airport to Guangzhou South Station by 7.00 am

I am arriving at Baiyun Airport at 4.30 am and I need to go to the South Station to buy train ticket and to catch the high speed train to Guiyang at 7.30 am. How early does the Line 3 start running from the airport and will it be able to arrive by 7.00 am ? Thanks