You're out of luck. Under the Singapore Immigration Act you are specifically prohibited under Part II, Sec. 8, Para 3d:
(d) any person who —
(i) has been convicted in any country or state of an offence for which a sentence of imprisonment has been passed for any term;
(ii) has not received a free pardon; and
(iii) by reason of the circumstances connected with that conviction is deemed by the Controller to be an undesirable immigrant;
Further on in Part V there are paragraphs describing the powers to deny disembarkation, or to detain.
I didn't find any reference to any form of limitations on these paragraphs, implying that they apply until the government changes the law to say they don't. There are some provisions for exemptions at the discretion of the Minister and/or Controller of Immigration - I doubt you'd qualify.
All that said, I am not a lawyer. If you seriously hope to be admitted legally to Singapore any time soon (or at all) you should find one.