The cheapest airline flying to Shenzhen is Air China. They are 71% cheaper than Singapore Airlines. (Average prices, based on 210 datapoints.)
At Shenzhen the most flights depart around 12:00. (Hourly flights, based on 351 datapoints.)
From Shenzhen most of the flights depart to Shanghai, second best connected from Shenzhen is Bangkok. (Daily flights, based on 82 datapoints.)