If he is appointed as a NMP?
The following article quoted Singapore Constitution, Art. 25(1).
http://en.wikipedia.org/wiki/Cabinet_of_Singapore#cite_note-Constitution_Art._25.281.29-22
The following article quoted Singapore Constitution, Art. 25(1).
The President also appoints other Ministers to the Cabinet from among the MPs, acting in accordance with the Prime Minister's advice.[23] Any MP, including a Non-Constituency Member of Parliament (NCMP) or a Nominated Member of Parliament (NMP), may be appointed a Minister. Thus it is possible for a person who was not elected by voters to be appointed by Parliament as an NMP, then by the President as a Minister.
http://en.wikipedia.org/wiki/Cabinet_of_Singapore#cite_note-Constitution_Art._25.281.29-22