For an overview of the Singapore legal system, other than consulting the Foreign Law Guide and the law library Country-by-Country Guide, these open-source research guides are helpful. See here, here and here.
The primary law of Singapore consists of its Constitution, statutes, subsidiary legislation, and case law. The law library does not subscribe to the fee-based database on Singapore law, LawNet, yet much of the recent primary law of Singapore is available freely on the web.
Statutes Singapore Statutes Online includes major constitutional documents and recent statutes but does not include subsidiary legislation. The Singapore Parliament website covers bills from 2002, selective committee reports from 2004, and parliament reports/debates.
Case Law LawNet, hosted by the Singapore Academy of Law, provides free access to the current three months of decisions and judgments rendered by the Subordinate Courts and the Supreme Court. The Academy website also includes Law Reform Reports. Singapore Law Reports which cover selective Supreme Court decisions are available in Lexis. Singapore Academy of Law Annual Review of Singapore cases, basically a discussion of cases selected from the Singapore Law Reports, is available in HeinOnline and in print.
EGov Portal EGazettes, the electronic version of the Singapore Government Gazette, is published daily and available for free public viewing for 5 days. The government information portal provides links to government departments and selective current legislation.
Current Awareness Singapore Law Watch, managed also by the Singapore Academy of Law, provides links and RSS feed subscription to legislative updates, recent judgments and commentaries. CommonLII covers selective legislation, judgments and secondary sources including the Singapore Yearbook of International Law.
For the law library print collection, treatises relating to the law of Singapore are shelved in the Lower East Side foreign law collection with the call number KPP.