He travelled widely as a painter, writer, filmmaker and human rights activist before he returned to Malaysia from Australia during the mid 90s, and practices laws at Cheah Kah Peng & Co., Penang.

In November 2015, Cheah with four other PKR Penang assemblypersons – Ong Chin Wen (Bukit Tengah), Dr Norlela Ariffin (Penanti), Dr T. Jayabalan (Batu Uban) and Lee Khai Loon (Machang Bubok) abstained from voting against a land reclamation motion proposed by the opposition United Malays National Organisation (UMNO); causing a conflict of the Pakatan Harapan (PH) state government and a strained relation with the Chief Minister of Penang then, Lim Guan Eng.

[10] In 2017, Cheah was excluded from the PH assemblypersons list, who were to register victims of the Penang's devastating floods on 4–5 November in their own constituency for the state's initiated post-flood relief aid of RM700 for every eligible recipient.

The Chief Minister Lim announced he together with the Pulau Tikus assemblyperson Yap Soo Huey instead would register floods victims in Cheah's Kebun Bunga constituency, near Botanical Gardens.

[12] As speculated, Cheah was dropped by PKR as the PH candidate,[13] to make way of the Kebun Bunga seat for the predecessor assemblyman, Jason Ong Khan Lee returning to contest the 2018 general election.