you can pass the clientname as comma seperated string as follows
'AA,BBB,CCC'
split that as a table and use to the IN query.
You can use following table function to split and create the table from your comma separated string
CREATE FUNCTION [dbo].[FT_CSVToTable]
(@CSVList varchar(8000) )
RETURNS
@tIDList TABLE (ClientName varchar(100) )
AS
BEGIN
WITH CSVCte (StartPos, EndPos) AS
( SELECT 1 AS StartPos, CHARINDEX(',' , @CSVList + ',') AS EndPos
UNION ALL
SELECT EndPos + 1 AS StartPos , CHARINDEX(',',@CSVList + ',' , EndPos + 1) AS EndPos FROM CSVCTE
WHERE CHARINDEX(',', @CSVList + ',', EndPos + 1) <> 0)
INSERT INTO @tIDList
SELECT SUBSTRING(@CSVList, StartPos,EndPos-StartPos) FROM CSVCte
RETURN
END
Then change your query as follows
SELECT RECORDID,AVAILABILITY,EMPLOYEMENTSTATUS,CLIENTNAME,DOB,SKILLS,EMAILID,VISA,CREATEDDATE,LOCATION,CITY+', '+C_STATE as LOCATION
FROM dbo.RECORDDETAILS where CLIENTNAME in (SELECT ClientName FROM dbo.FT_CSVToTable(@clientname))