How can i go by taxi from HK airpot to regal palace hotel in dongguan, ?

It is impossible to take a taxi from the airport to Regal Palace Hotel in DG directly unless you book a pick-up service.
In my opinion, you can take the airport shuttle bus to reach Houjie International Hotel and then take a taxi to your hotel. From Houjie International Hotel to your hotel, there is about 4km.