I tend to disagree with horangi here, it is not easy as such.
I am a PR here now: Married a Singaporean woman in Singapore, then we went back to The Netherlands, my homecountry (she applied and received a permit to stay and live in Holland).
We didnot like it and we then decided to come back to Singapore. Now my wife got herself a job again easily, so she had a Singapore income, when we applied for my PR. I applied for the Singapore PR, whilst being in Holland. You can get the application forms from the Singapore embassy in your country of residence. Although the Singapore authorities will not exactly tell you what the criteria are, it is important that your history shows good credentials, no criminal past, good income history (very subjective that is) and good education (also not defined in detail).
When the authorities here in Singapore decide that you will contribute to the growth of Singapore (income, education AND FUTURE KIDS), your PR will be Approved in Principle. With the AiP PR, you can then come to Singapore and either apply for the "full" PR by having your wife to "sponsor" you (she has to have a more than average income to support both of you), or you get your "full" PR when you manage to find a job. As soon as you have the job, you will get it as well, in case you do not chose for the "sponsoring" option through your wife.
Note: It is by NO means an automatic process, in fact you will be told very careful, when registering for you marriage here in Singapore (ROM), that the marriage as such will give you NO rights to stay and live in Singapore. You will sign for that.
Basically: getting married, have a good education, good income history and produce kids for Singapore, that's all it takes for a PR here
And yes, you will have to do your NS as well, if not older than 35 years of age.
good luck!
Eric