So if you do not wish for that to happen, do up a simple will. You do not need to have a lawyer as long you are above 21 years old, or working in a high risk profession, but of course if you have the money, do go ahead and engage one. If you are rich enough, get the lawyer and keep the will for you. If not, do like I do, write up a will, get 2 witness to see you sign and they sign themselves with NRIC no. and full name so they can come forth and clarify any doubts. Then, hand over this will to someone you can trust, or your mother to safe keep. There is no point keeping it in a secret location nobody knows about.
I have attached a sample will written by a lawyer in Singapore sometime back, updated it, got 2 close friends to sign, sealed it and hand over to someone. Do use it, amend it to your circumstances but keep it understandable.
Last but not least, do update it constantly if your spouse keep changing.