Wei Na Sim is a counsel in the Litigation & Dispute Resolution practice in Mayer Brown's Hong Kong office.

Wei Na advises and acts for companies in litigation, investigations and regulatory matters, with a focus on the financial services industry. Wei Na has substantial experience supporting banks in multi-jurisdictional financial crime compliance reviews conducted by monitors in Asia, Europe and the US. She also advises clients on environment, social and governance (ESG) related matters and is a regular contributor to the firm's ESG blog

Wei Na has in-house legal counsel experience from a secondment with the Asia Pacific headquarters of an international bank. Further, Wei Na has litigation experience from private practice in Singapore where she advised and represented public listed companies from a variety of industries, banks, insurers and capital market intermediaries in complex commercial disputes and regulatory matters.

Euromoney's Rising Stars Expert Guides (2022) recognized Wei Na as a rising star for White Collar Crime, Hong Kong.

Wei Na is a pro bono ambassador and NextGen committee member in Mayer Brown's Hong Kong office and is actively involved in diversity and inclusive initiatives. Wei Na speaks English and Mandarin.

Spoken Languages

  • English
  • Mandarin


Financial Services Regulatory Advisory

  • Advised an international bank and on all legal and regulatory aspects on a broad range of high-profile financial crime related reviews and associated activities. Collaborated with subject matter experts from the bank to mitigate the risks of extraction, storage and production of large, complex datasets, providing onsite support during the reviews and advising on sensitive geo-political issues. 
  • Provided strategic advice to an international bank on legal, regulatory and reputational risks arising from the publication of leaked documents by investigative journalists.
  • Advised an international bank in the drafting and negotiation of required contractual arrangements and obtained regulatory approvals for the appointment of an Independent Consultant to conduct annual OFAC (Office of Foreign Assets Control) compliance reviews.
  • Advised an international bank on data privacy issues in support of the bank's enhancement of its global financial crime data sharing framework for multinational corporations. Advised on updates to the bank's policies and procedures.
  • Advised the Hong Kong branches of global financial institutions on queries received from the Securities and Futures Commission and the Hong Kong Monetary Authority.
  • Advised the Hong Kong branch of a South East Asian headquartered bank on compliance with the Hong Kong Code of Conduct for Persons Licensed by or Registered with the Securities and Futures Commission.
  • Advised a Hong Kong asset management company on its ESG policy and conducted a gap analysis against the Securities and Futures Commission's climate-related risk requirements in the Fund Manager Code of Conduct.
  • Advised various financial institutions on matters concerning anti-money laundering laws in Singapore including issues on suspicious transaction reporting, obligations to name beneficial owners of bank accounts and parties in wire transfers as well as customer due diligence requirements.
  • Acted for a securities company to respond in a show cause matter instituted by the Singapore Exchange in respect of breaches of trading restrictions on certain securities.
  • Advised several banks with operations in Singapore on issues concerning secrecy obligations under the Singapore Banking Act and the Singapore Trust Companies Act in the context of requests for documents from foreign prosecution authorities.
  • Advised a major life insurance and asset management company on Singapore law issues relating to the implementation of the U.S. Foreign Account Tax and Compliance Act by its local businesses. Co-ordinated the appointment of local counsel and the collation and review of local law advice from multiple Asian jurisdictions.

Banking and Financial Services Disputes

  • Represented an international bank in a high-profile claim commenced by a foreign individual in the Hong Kong Court of First Instance for Norwich Pharmacal and section 21, Evidence Ordinance (Cap. 8) orders. 
  • Represented several international banks in suits commenced by high net worth clients in the Singapore Supreme Court to recover losses sustained from investments during the global financial crisis.
  • Represented a BVI private investment company in a claim filed in the Singapore High Court against an international bank to claim for losses suffered by the client pursuant to several margin calls made by the bank.
  • Acted for a Middle Eastern bank in a suit commenced by a Singapore listed infrastructure and projects company to restrain the bank from making payment to a third party bank under counter guarantees governed by the URDG 458 and English law.
  • Acted for a trust company in a claim commenced by an individual in the Singapore High Court for an alleged inter vivos gift by the trust company’s deceased client to the claimant.


National University of Singapore, LLB (Hons)


  • Hong Kong
  • England and Wales
  • Singapore


  • Member, Women in Law Hong Kong
  • Member, Women’s White Collar Defense Association
  • Member, Singapore Institute of Arbitration
  • Associate Mediator, Singapore Mediation Centre
  • Member, Singapore Chamber of Commerce Hong Kong
  • Rising Star - White Collar Crime, Hong Kong SAR – Rising Stars Expert Guide (2022)