It is really difficult to find a place in Singapore that has clear 360-degree views mostly away from streetlights or other sources of light pollutions.
Kranji Park Car park B. Too many trees. Less light pollution towards the west.
Bahtera Track deep in Lim Chu Kang: less affected by lights (this dirt road is unilluminated) but the low-altitude skies are mostly blocked by the tall plantations. Better views towards the west.
Eastern ends of East Coast Park (NSRCC, National Sailing Centre, etc...) -- unblocked views in the directions from east to south. Other directions are all terribly light-polluted.
Changi Beach Park -- better views towards north and east; blocked views/terrible light pollutions in other directions
But recently I found a nice place that lets you have a 360-degree clear view of the skies -- and some relatively darker skies to the north and to the north-east. It is a large open flat field.
https://goo.gl/maps/csjvoLuuTJKgwWiTA