Note 10 - Restricted Net Assets (Details Textual) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Restricted Net Assets	$ 0	$ 0

Total net assets that cannot be used for operating purposes because of contract or regulatory requirements that are in effect for a period that extends beyond one year.

No definition available.

Name:	bysi_RestrictedNetAssets
Namespace Prefix:	bysi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant