SINGAPORE - Former presidential candidate and general practitioner Tan Cheng Bock is hanging up his stethoscope after 50 years in medicine.

"I always say that medicine is my love, but politics is my calling," said Dr Tan in a Facebook post on Monday (Dec 31), adding that he looks forward to serving Singapore "in a new way". He added: "The country and the peoples' welfare are my top priority."

In July, seven opposition parties met to discuss the possibility of forming a coalition to contest the next general election, which must be held by April 2021. They invited Dr Tan, a former People's Action Party MP, to lead this coalition.

At the time, Dr Tan said: "I think I must help, but in what capacity, I have not decided."

In his post, Dr Tan recounted how he opened his first clinic - Ama Keng Clinic - in 1971 in a village where houses were topped with attap and zinc roofs, and water came from wells and standpipes.

Most homes did not have electricity and villagers made do with kerosene lamps, said Dr Tan, recalling how he once delivered a baby by dim kerosene lamplight. To the villagers, Dr Tan said, he became "more than a doctor, by helping them in family feuds, land disputes and writing letters to government departments".

Dr Tan said that the villagers were subsequently scattered across Singapore following a large-scale resettlement exercise, which was "extremely traumatic and painful for many" as their only life skill was farming.

"They suffered anxiety and depression settling into Housing Board (HDB) flats," he said. "Now the village is no more and overgrown with secondary forest."

Many of his old patients continued to seek him out after he moved his practice to the HDB heartlands, Dr Tan said, adding that some have asked him what he plans to do.

"I tell them that retirement is not an option for me - I am merely switching my role from serving patients to serving people," he said.