Find the bus station in the southwest direction across the road from the entrance of the memorial hall, take bus 139, and ride for ten minutes to the end, which is Toa Payoh MRT station (NS19 TOA PAYOH). Take the subway here, the red line (North-South Line), and go to Marina

Take the South Pier direction (southbound) subway and get off at NS25/EW13 City Hall, walk directly to the platform opposite the platform, transfer there to the Green Line (East-West Line), heading towards Pasir Ris/Changi Airport (eastbound)

Take the EW4 TANAH MERAH, get off and walk to the middle platform, wait for the subway to the airport, get on and ride to the end, you will be at the airport in less than ten minutes. Another way is to get to Toa Payoh MRT station and take the northbound subway.

(Jurong east direction), take two stops to EW17 Bishan, get off at the bus terminal next to the subway station, and take bus No. 53, which will take you directly to the airport.

But it will be slower than the subway.