A Singapore Civil Defence Force (SCDF) officer testified that hours before Corporal Kok Yuen Chin was pushed into a fire station pump well on May 13 last year, another colleague had tried to "kolam" him.

However, when pressed on the details, he said he could have remembered wrongly.

Taking the stand during a trial where two SCDF officers linked to Cpl Kok's death are contesting charges against them, First Warrant Officer Mulifatullah Atan said one of the men on trial, rota commander Kenneth Chong Chee Boon, had stepped in to stop it.

But among the various points he made, he was unable to back some up or said he had remembered the details wrongly when grilled during cross-examination.

On the night of May 13 last year, Cpl Kok, 22, drowned after he was pushed into the Tuas View Fire Station pump well, or kolam, in a ragging ritual that was part of activities to mark the completion of his national service.

WO1 Mulifatullah said that about four hours before this, they were playing football and Staff Sergeant Al-Khudaifi Chang had held on to Cpl Kok and said the word "kolam" to get the full-time national serviceman to enter the nearby pump well.

He thought Staff Sgt Chang would have made Cpl Kok enter the well based on his actions and mention of kolam.

Chong's defence lawyer, Mr Wee Pan Lee, pressed him on this and brought up differing testimony by Staff Sgt Chang. On Monday, Staff Sgt Chang testified that he got into a "friendly tussle" with Cpl Kok during the game, but did not mention having said the word "kolam" then.

This prompted WO1 Mulifatullah to say: "I heard someone mention kolam... but I don't remember if he's the one."

The ongoing trial involves Chong, 38, a lieutenant, and Nazhan Mohamed Nazi, 40, a first senior warrant officer who was deputy rota commander. The two were in charge of the station that night.

They were each charged with aiding a rash act that caused grievous hurt by illegal omission. The two had allegedly failed to prevent a group of officers from making Cpl Kok enter the pump well, thereby endangering his life.

That evening, the servicemen on duty had gathered in the fire station's control room to hold a cake-cutting ceremony for Cpl Kok.

WO1 Mulifatullah said he left the room after the celebration and was speaking with Nazhan outside. When he returned, he saw Chong and Sergeant Mohamed Hanis Mohamed Hussain there.

On Wednesday, however, Sgt Hanis testified that he had left the room during the ceremony and when he returned, only Chong was there. He did not mention WO1 Mulifatullah.

When Mr Wee asked whose version the court should accept, WO1 Mulifatullah said that he could not remember if Sgt Hanis had been there.

Said Mr Wee: "You have asserted something you could have been mistaken about. Having said that he was there, and now saying he was not there, this raises questions about which part of your evidence is like that too."

That night, some officers carried Cpl Kok across the yard towards the pump well, and WO1 Mulifatullah was among those gathered there.

The defence also tried to poke holes in WO1 Mulifatullah's statement that he had seen Cpl Kok flash an "unwilling" smile moments before he was pushed into the pump well.

Nazhan's lawyer, Mr Singa Retnam, asked: "He took his shirt off and sat down by himself without anyone physically forcing him to, how do you know he was unwilling?"

WO1 Mulifatullah said: "It was more of my opinion when I saw him in that moment."

The trial continues today.