The Constitution page of Singapore Statutes Online (open access) links to the current Constitution - the official 1999 Revised Edition, with unofficial amendments to date.
The Constitution is the supreme law of Singapore (Article 4).
Amendments to the Constitution are provided for in Articles 5 and 8. Most provisions can be amended by a law enacted by the Legislature (Article 5), but any amendment to Part IV - Fundamental Liberties - can only be made by the Legislature following a national referendum (Article 8).
The enactment of the Constitution was complicated. After independence from Britain in 1963, Singapore joined the Federation of Malaya and enacted the State Constitution of 1963. In 1965 Singapore ceased to be a state of Malaysia and became an independent and sovereign state. As a result, the Constitution of the newly independent Republic of Singapore was found in three separate documents: the Republic of Singapore Independence Act 1965, the State Constitution of Singapore as amended in 1965, and provisions of the Federal Constitution of Malaysia as made applicable by the Republic of Singapore Independence Act. In 1979 a consolidated reprint of the Constitution was finally enacted, integrating the provisions of the three Acts and Constitutions into one document. Further reprints of the Singapore Constitution were published in 1987 and 1992. The current Reprint was issued in 1999. It has been amended many times since.
The section on Singapore includes the following chapter:
Please note that much of this commentary is only current up to the 2008 amendments.
The International Encyclopedia of Laws: Constitutional Law (UniMelb staff & student access) contains a useful history and detailed commentary on the Singapore Constitution, including references to cases. Scroll to Singapore under the 'National Monographs' heading.
Jhaveri, Swati and Neo, Jaclyn L, 'The Many Facets of Constitutional Dialogue: The Case of Singapore' (2017) 18(1) Australian Journal of Asian Law 1
Neo, Jaclyn L, 'Secular Constitutionalism in Singapore: Between Equality and Hierarchy' (2016) 5(3) Oxford Journal of Law and Religion 431-456
Silverstein, Gordon, 'Singapore's Constitutionalism: A Model, But of What Sort?' (2015) 100 Cornell Law Review 1
Neo, Jaclyn L, 'The Constitution and the Protection of Minorities: A Judicious Balance?' (2008) in Thio Li-ann & Kevin YL Tan (eds), Evolution of a Revolution: Forty Years of the Singapore Constitution (Routledge-Cavendish, 2008)
HEIN Online World Constitutions Illustrated: Singapore (UniMelb staff & student access) includes:
Please note that much of this commentary is quite old, and maybe more useful for historical rather than contemporary research.
Li-ann Thio, A Treatise on Singapore Constitutional Law (Academy Publishing, 2012) KT 3669 THIO
Use LawNet (UniMelb staff & student access).
The Constitution provides for a specialised Constitutional Tribunal (Article 100). The Tribunal consists of at least three judges of the Supreme Court and has limited jurisdiction. The President may refer to the Tribunal any question as to the effect of a constitutional provision which has arisen or is likely to arise and in particular the question of the constitutional validity of a bill before Parliament. The opinion of the Tribunal on the interpretation of the Constitution, and on the constitutional validity of the law, is binding on all courts (Article 100(4)). Ordinary citizens and members of the parliamentary opposition do not have the right to submit constitutional issues to the Tribunal.
The Tribunal has no power to deal with complaints about fundamental rights. Therefore, the protection of the fundamental liberties guaranteed in Part IV of the Constitution is dealt with by the ordinary courts. They have the power to strike down unconstitutional legislation (Article 4) and to regulate executive action through the application of administrative law remedies.
Source: Rainer Grote, 'The Republic of Singapore: Introductory Note' in Oxford Constitutions of the World (UniMelb staff & student access). See this commentary for more detailed information on judicial review of the Constitution.
See also:
Jhaveri, Swati, 'Advancing Constitutional Justice in Singapore: Enhancing Access and Standing in Judicial Review Cases' (2017) Singapore Journal of Legal Studies 53-76. Available on open access on SSRN.
Ong, Benjamin Joshua, 'The Doctrine of Severability in Constitutional Review: A Perspective from Singapore' (2018) Statute Law Review Available on open access on SSRN.
Constitutional Interpretation in Singapore by 
