As always, the best ource of information is Citizenship and Immigration Canada's web site:
Welcome Page | Page d'accueil
Here's a quick overview of what your options are.
Once you're married and your wife is legally in Canada on a visitor visa, you have the option of applying for Permanent Resident's status from either inside Canada or from abroad.
To apply from abroad, your wife would return to Singapore and make the application from there. She would remain in Singapore until such time as a decision is reached on her case. If she is accepted for PR status, she'll be notified and given a certain time frame to land in Canada.
If you decide to apply from within Canada, the two of you will need to fill out the appropriate forms and file them, along with the fees, with CIC. Time frames for processing of applications are available at CIC's site
Because your wife will have entered the country on a visitor visa, she will not be allowed to legally work until she has been accepted as a PR. Depending on your province of residence she may not be eligible for provincial health coverage while on a visitor visa. CIC makes it very clear that if a person with a PR application in process leaves Canada, there is no legal guarantee that they will be allowed to re-enter.
It is very important that a person with a PR application in process makes sure to keep their visa valid. This means she'll likely have to apply for at least one extension for her visitor visa. Be sure to allow plenty of time for extension application to be processed.
After all the hoops have been jumped through, a decison is rendered regarding the application. If she is accepted, she'll be issued a Social Insurance Number and be permitted to work. If for some reason she is rejected, she will be required to leave Canada.
Please take the time to plow through the various bulletins and forms available on CIC's site. The process isn't overly difficult, but it's important that yoou fully understand all the requirements and file all the paperwork correctly. Incorrect information can lead to the application being sent back for correction and then being returned to the starting point of the process.