A short 3 day trip to Guilin and Yangshuo in Guanxi province in China.
From Hong Kong a 40 min cross border bus to Shenzhen. From Shenzhen to Guilin by night service sleeper bus. If you have time and don’t have to rush after office, you may board the high speed train to Guilin North from Shenzhen or Guangzhou.
It is suggested to have a guide as people hardly speak English there. Guide is not much costly around 50 USD per day. They will have a sedan or SUV depending on the number of people in your group.