Wei Na Sim is a counsel at Mayer Brown’s Hong Kong office. Wei Na specialises in litigation and investigations with a focus in financial services related matters. Prior to joining Mayer Brown, Wei Na practised in Singapore for more than nine years where she advised and represented public listed companies, banks, insurers, financial institutions and intermediaries and inter-dealer brokers in matters at all levels of the courts of Singapore involving novel issues of law, in a multi-jurisdictional context.

Wei Na completed a secondment with an international bank in 2017. She was the country legal lead working with a team from Mayer Brown in several reviews in Asia conducted by an independent corporate compliance monitor appointed pursuant to a deferred prosecution agreement.

Spoken Languages

  • English
  • Mandarin
  • Cantonese


Financial Services Regulatory Advisory

  • 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 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 Taiwanese scientist in litigation in the Singapore Supreme Court against a European private bank in respect of multi-million losses sustained from leveraged share forward accumulators.
  • 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
  • Associate Member, Chartered Institute of Arbitration
  • Member, Singapore Institute of Arbitration