Polling Day 2015, Public Holiday

It was declared that 11 September 2015 as Public Holiday in Singapore, also a polling day. 

Can you don't come to work if employer ask to?
Hey come on, it is your Public Holiday ! Under the Holiday Act (1998) Clause 6 (Holiday in substitution of Public Holiday) - "Nothing in this Act shall prevent or affect the validity of any agreement made between any employer with any of his employees giving the employee any other holiday or holidays in substitution for any one or more public holidays." 

I guess the key word here is "agreement" ... 

In short, can your employer 'force' you to work overtime or replace you with another day of annual leave, I guess the answer is "NO" unless you agree with it.

It is important to serve the right of citizen, you may want to ask PM on suggestion, if your employer insist you to work, right? :)

What if you on Medical Leave on the day?
Well, if your employer has replaced the Public Holiday with another day of Annual Leave (Public Holiday In Lieu), your medical leave on 11 September will still be treated as another day of MC, but of course, you shall still eligible for additional day of the Annual Leave (Public Holiday In Lieu) credited.  

However, your employer request you to come back to work as overtime on the day, you can go for your medical leave, to serve as a reason for not performing overtime. 
No Medical Leave (MC) shall be deducted from your eligibility!