Accrued charges and deposits (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Accrued Charges And Deposits Details 1Abstract
Provision for individual income tax underpaid penalty	$ 1,893	$ 1,893
Accrued provision for severance payment	568	444
Accrued audit fee	160	160
Accrued salary and wages	124	313
Other	420	364
Total	$ 3,165	$ 3,174

Amount of expense for salary and wage arising from service rendered by nonofficer employee. Excludes allocated cost, labor-related nonsalary expense, and direct and overhead labor cost included in cost of good and service sold.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(4))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Name:	us-gaap_SalariesAndWages
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration