Poon was born and raised in Hong Kong. He studied economics at the North Carolina A&T State University before he returned and worked in Hong Kong in 1978. He had worked for the Kowloon Motor Bus Ltd. as public relations consultant. He began to participate in community services in 1979 by working in the area committees in Kwun Tong district. He was subsequently appointed to the Kwun Tong District Board in 1985 and elected to the Legislative Council in the first indirect election in 1985 through Kwun Tong electoral college constituency consisting of members of the Kwun Tong District Board and reelected in 1988.
