The monkey, which appears to be a long-tailed macaque, had wandered into Lakeside MRT for some reason, and seemed unafraid/oblivious to the passengers in the station.
Wildlife rescue group Acres actually proposed a method back in 2014, called monkey herding, to keep the primates away from residential areas in Singapore.
It involves stationing a specially trained guard at monkey hotspots in Singapore to shoo monkeys away from residential areas.
The guard is supposed to use nets, sticks to deter the monkeys from entering residential areas.
Well, looks like either that plan was scrapped long ago, or the monkey somehow managed to bypass all the guards.
At least it managed to get a glimpse of what Singaporeans have to face in public transport every day: