I solved this one in the following manner.
I wrote my previous employer the following email:
Dear Bob,
I am applying to become a permanent resident of Singapore. Amongst the documentation they require is a 'testimonial stating the nature and duration of employment and also the last drawn basic salary'.
Below, I have described the nature of my work, my position title, duration, and my final salary. If you agree with this, would you please reply, with a copy of this email, with words to the effect: "The information as stated by Strong Eagle is correct", along with your name, title and contact number.
In working for the Frammis Flapjack Company, I held the position of Senior Procrastinator. I held this position from June, 1908, until July 2001. In this position, I advised the company as to how best to avoid doing any project that would actually accomplish anything. My final salary upon resigning from the company was US$ 3 million per month.
******
I sent this email (obviously with real job description), got a response, printed it out, and it was accepted without a peep.