How to use IN clause in THEN part of CASE statement without errors?

I want to use IN Clause in Then part of CASE statement. This is giving me some errors.

declare @Role varchar(10),@Region_Code varchar(100)
set @Role='AB'
SEt @Region_Code='003,002,004,005'

select * from [tableName] BM
where CASE WHEN @Role='AB'
THEN BM.[Region code] in (Select * from dbo.Split (@Region_Code, ','))  
WHEN @Role='XYZ'
THEN BM.Branch_code  in   (Select * from dbo.Split (@Region_Code, ','))
end

Solved

Why not use IF ELSE IF statement

IF @Role='AB'
  select * from [tableName] BM
  where  BM.[Region code] in (Select RegionCode from dbo.Split (@Region_Code, ',')) 
ELSE IF  @Role='XYZ'
  select * from [tableName] BM
  where  BM.[Branch_code] in (Select RegionCode from dbo.Split (@Region_Code, ',')) 

Also try this

select * from [tableName] BM
where ( @Role='AB' AND BM.[Region code] in (Select RegionCode from dbo.Split(@Region_Code, ','))  )
OR
 ( @Role='XYZ'
AND BM.Branch_code  in   (Select RegionCode from dbo.Split (@Region_Code, ','))
)