
Hi Peerapong,
Good day and welcome to the community!
To allow access without sign-in for shared files on SharePoint for your users, you would need to set the external sharing from both the organizational level and the site level. Please notice that this may require administrative role to complete the settings.
The external sharing level needed to be configured at least at the level of 'Anyone' to allow any external users to access without signing.
For more information, you can also refer to this official article: Manage sharing settings for SharePoint and OneDrive in Microsoft 365 - SharePoint in Microsoft 365 | Microsoft Learn.
I hope this can help!
Best regards,
Katherine V - MSFT | Microsoft Community Support Specialist