You should search for the potential digital marketing company singapore on forums, reviews, or blogs. Do not shy away from asking the forums specific questions about the potential SEO agency. It would be essential to get a viewpoint about them from reliable sources. You would be surprised to find plenty of information online.
You should look for their performance online. There should be conclusive proof of their competency as an SEO agency. If the potential SEO agency has been promoting several businesses, they would have the experience and knowledge about SEO. They must have several businesses they worked on ranked higher on the popular search engine results pages.