You must leave your mobile phone with Presiding Officer (KTM) before you vote

In GE15, the EC introduced a new procedure when you enter your polling stream (saluran) to vote. After you have collected your ballot paper, you are required to leave your mobile phone in a tray on the KTM’s desk and proceed to the voting both. After you have dropped your ballot into the box, you can collect your phone on the way out. This is to prevent people from taking a photo of their ballot in order to claim money from those who are buying votes. It is also an offence under Section 3 of the Election Offences Act to reveal your vote to others as a vote is supposed to be secret.

News report: https://m.malaysiakini.com/news/643322