To show proof of your marriage to the relevant authority overseas, you may consider applying for a digital copy of the duplicate marriage certificate and you will receive a digital extract copy via email. The overseas authority may verify the document by scanning the QR code on it. 

In the event the overseas authority requires the digital copy to be legalised, you may contact the Singapore Academy of Law (SAL) for assistance. For more information, you may visit SAL's website and click the tab "News & Events" for details on the process and procedures.