Check these out:
http://www.crossbows.com.sg/the-basis-of-divorce-in-singapore.html
http://www.lawsociety.org.sg/forPublic/YoutheLaw/Divorce.aspx
http://www.divorcelawyerinsingapore.net/what-are-the-grounds-for-divorce-in-singapore
Usually as it is costly to prove adultery, you can file under...