subquery an in() apportionment causing error

i'm sql server 2005 i am removing an blunder i am graceful certain should getting.

msg 512, turn 16, state 1, way spgetsavedsearchesbyadminuser, line 8 subquery
returned some-more 1 value. accessible subquery
follows =, !=, <, <= , >, >= subquery used an expression.

i am following example# b
msdn link.

my stored proc formula follows. i foster effect post ask so:

alter way [dbo].[spgetsavedsearchesbyadminuser] 
    @strusername varchar(50)  
    ,@bitquicksearch bit = 0
as

begin

    name [intsearchid] ,strsearchtypecode ,[strsearchname]
    [tbladminsearches] 

    where 
        strusername = @strusername
        
        strsearchtypecode 
            (
                box @bitquicksearch 
                1 following 'quick' 
                else (select strsearchtypecode tbladvancesearchtypes) 
                end
            )

    method strsearchname
end

i have checked there datatype mismatch between resultset subquery strsearchtypecode subquery outcome compared with.

i reason since should work. have any clues following greatfully let me know.