Is Fort Siloso haunted?
Singapore Reported haunting level 2 of 5

What actually happened
On 14 February 1942, during the Battle for Singapore, the British deliberately destroyed the fort's battery; under the Japanese Occupation the fort held Australian and British prisoners of war.
The history
Built in 1878 on Mount Siloso to protect New Harbour, it was among the first forts in the world to adopt the open artillery battery design; it has been a military museum since 1974 and was gazetted a National Monument on 15 February 2022.
What people report
Visitors have reported footsteps and figures in the tunnels and gun positions, and local tradition links them to the fort's wartime prisoners.
That paragraph is reported tradition, not a claim about what is there. The history above it is sourced; the stories are recorded because people tell them.
Visiting
Siloso Road, Sentosa, Singapore 099981