Employment Act (Chapter 91): Primary employment legislation in Singapore that should be considered even for non-binding documents. Any references to employment terms or achievements should align with legal working practices defined in this Act.

Personal Data Protection Act (PDPA): Governs the collection, use, and disclosure of personal data. Relevant when including personal information in the appreciation letter, especially if there's potential for public sharing.

Prevention of Harassment Act (POHA): Ensures that communication remains professional and cannot be interpreted as harassment. Guidelines for appropriate language and behavior in professional communications.

Industrial Relations Act: Relevant for unionized employees, governing the relationship between employers and unions. Consider any union agreements regarding formal communications.

Company Policies: Internal guidelines and protocols for official documentation and communication that must be followed when drafting company documents.

Professional Standards: Guidelines for maintaining appropriate professional tone and avoiding language that could be interpreted as creating contractual obligations.

Cultural Sensitivity Guidelines: Considerations for Singapore's multicultural environment, ensuring appropriate language and references that respect diverse cultural backgrounds.