Yes, you do need a VDA license if you're accessing a virtual desktop running a Windows desktop OS. There is one scenario where you don't need a license and that is If the Windows workstation/PC you are accessing the Virtual Desktop has software assurance t
Many people will use Windows Server operating system as a desktop. This doesn't require a VDA license.
You will need a MS VDA subscription if you are accessing your VM desktop using a zero client - i think they are annual or 3yrly . As techguy explains below you don't if your thin/thick client is running a licensed version of windows.