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 enforcement matters, with a focus on the financial services industry. Wei Na is experienced with handling independent compliance monitor reviews conducted on banks in Asia, Europe and the US. Wei Na also has in-house legal counsel experience from secondment with an international bank where she worked on financial crime compliance issues relating to anti-money laundering and sanctions. 

Prior to joining Mayer Brown, Wei Na practiced litigation in Singapore where she advised and represented public listed companies, banks, insurers and financial institution intermediaries in complex commercial disputes and financial services related matters. Wei Na handled litigation at all levels of the courts of Singapore and represented clients in mediation. Wei Na also advised clients on regulatory matters such as show cause requests from Singapore regulators, requests for evidence from foreign regulators and advised on customer due diligence requirements, anti-money laundering and confidentiality laws. 

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

Spoken Languages

  • English
  • Mandarin


Financial Services Regulatory Advisory

  • Assisted an international bank to draft all required contractual arrangements and obtain regulatory approvals for the appointment of an Independent Consultant who will conduct annual OFAC (Office of Foreign Assets Control) compliance reviews for the bank.
  • 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. This includes working with subject matter experts from the bank to assist 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 on data privacy issues in support of the bank's enhancement of its global financial crime data sharing framework for multinational corporations. This includes providing input on the bank's policies and procedures.
  • 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.
  • Assisted 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 the Singapore office of a European bank on issues associated with an internal review that was conducted by an independent firm pursuant to a directive issued by the Monetary Authority of Singapore.
  • 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. Also assisted the client to co-ordinate 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, Bachelor of Laws
Second Upper Honours


  • Hong Kong
  • England and Wales
  • Singapore


  • Associate Mediator, Singapore Mediation Centre
  • Member, Singapore Institute of Arbitration
  • Member, Women in Law Hong Kong
  • Member, Women’s White Collar Defense Association