A man originally accused of causing grievous hurt to his elderly adoptive father has now been charged with his murder.

Su Caizhi, 28, was hauled to court on Jan 2 for seriously hurting Mr Pang Tee Lin, 72, at their Bedok Reservoir Road flat on New Year's Eve. Mr Pang died on Jan 9.

Last Friday, the prosecution decided to amend the charge against Su to murder, accusing him of causing Mr Pang's death between 7.25am on Dec 31 and 1.28pm on Jan 9.

Su registered a commodities trading business in 2014 under his adoptive name, Pang Kee Kiang.

According to Chinese evening paper Shin Min Daily News, Mr Pang and his wife adopted Su when he was five years old and staying at an orphanage in Hainan, China.

They named him Pang Kee Kiang. Until two years ago, the couple ran a food stall, which they later sold.

A lawyer appeared for Su at last week's hearing. Su is being remanded at Complex Medical Centre in Changi pending a psychiatric report on Feb 4.