Do many hong Kong people go to Thailand and pray to the 4 Face Buddha?Do HK ppl install 4 face buddha at home?

No, most Buddhists in Hong Kong, as well as Japan, worship "Guan Yin", they rarely go to Thailand to worship the four-faced Buddha as it is not popular in Hong Kong. On a side note, I think most of them do go to Kinmen to visit the temple of blessing. The four-faced Buddha is called "Phra Phom", it's a popular Thai version of Bhrama derived from Hindu culture. In Mainland China, the more popular Buddha is "Budai" or the man with a big smile and big belly.