Resignation letters come in numerous guises but the most important factor to consider is to keep it short, simple and to the point. Do not be tempted to put anything down in writing that may come to regret, especially when you require references or have a final salary to come.

While writing and submitting a resignation letter may be an unpleasant task, there really is nothing to it. There is no need to go into detail about your reasons for leaving as these may be open to misinterpretation and could lead to difficulty when your references are applied, for example :
While I enjoyed the job at ABC Engineering, I found that my daily tasks had become repetitive.
This could easily end up in a verbal or written reference as “James Tan was easily bored by repetitive task.”
It is also inappropriate to use the resignation letter to tell your boss where you are going, what you are doing in your next job, or how much you will be making.
It is sufficient simply to state that you are submitting your resignation with effect from X and intend your final date of employment to be Y ( normally several weeks in advance or as stated in your contract of employment ).
Sample Resignation Letter
4 May 2012
Mr. Vincent Chan
Process Manager
ABC Engineering Pte Ltd
59 International Road
Singapore 100059
Dear Mr. Chan
After careful deliberation, I am giving notice of my resignation from ABC Engineering with effect from 4 May 2012.
I appreciate the work we have been able to accomplish together at ABC Engineering for which I have enjoyed. Please be assured that I will assist to the best of my abilities in the smooth transfer of my duties.
I wish you and the company continued success in the future.
Yours sincerely
TanKSJames
James Tan Kok Seng