Bangkok - Xiamen - Hong Kong

Hello,

I am holding a Greek passport (EU citizen) and in 10 days I will be travelling from Bangkok to Xiamen with a direct flight by Xiamen Airlines. Then after two days I am traveling from Xiamen to Hong Kong with a direct flight by Cathay Dragon. Am I eligible for the 72 hour free transit? If so, what should I do, should I request one in advance?

Thanks in advance.