With the seat vacant, the Election Commission will have to call another by-election within 60 days - the eight of such polls since March 2008 general elections.
Permatang Pasir, which is one of three state seats in PKR leader Anwar Ibrahim's Permatang Pauh parliamentary constituency, is the sole PAS seat in Penang.
In the last general elections, Mohd Hamdan, who bagged 11,004 votes, defeated Ahmad Sahar Shuib from Umno (5,571) by a majority of 5,433 votes.
Only two months ago, Penanti - a state seat next to Permatang Pasir - had a by-election following the resignation of then PKR state representative Mohammad Fairus Khairuddin.
The by-election, which was won by PKR's Dr Mansor Othman, saw one of the lowest voter turnout when rival Umno opted not to contest the polls.
The upcoming by-election will be the third by-elections in the Permatang Puah constituency in less than one year - the first being Anwar's victory in August last year after his wife, PKR president Dr Wan Azizah Wan Ismail, quit the seat.