I will arrive HK airport at 15.00 hrs. Plan to go Chaoyang. Anyone could recommend how to take bus and the duration, fare ?

There is a direct corss-border coach from HKIA to Chaoyang, but it leaves around 07:00 in the morning. You will miss it.

By bus, you can take the coach leaving around 18:00 to Shanwei in around 4.5h and the bus fare is HK$280 per person. At Shanwei Bus Station, I remember there are direct buses to Chaoyang.

Or you can take a plane from HKIA to Chaoshan Airport, where there are direct buses to your destination.