Google focus group discussion and you shld be able to find. Look in gumtree singapore. Sometimes they advertised. The lowest i got paid was $30 and the highest was $150.

Mystery shopping also helps. That can also be googled. The lowest pay i got was $8/assignment in a fast food and highest was $250/assignment for a bank. I did pretty well that the research company sponsored me an air ticket to bangkok to mystery shopped a few shops in downtown as well as in the departure hall of bangkok airport. The beauty of this is that you can do it in a timing you are comfortable. but the difficulty is the lengthy report you had to write.

Fast food mystery shopping is easy but the payout is low. But then again u get to eat for free. So that helps to pay for my meals when i am jobless.

Mystery shopping cannot substitute a full job income but it can supplement if you can accumulate anything between 20-25 assignments a month. That works out to be anything between $300-$600 extra depending on the payout.