1. using string comparison technique

SELECT a.*
FROM tableA a
INNER JOIN tableB b
WHERE ',' + b.AssetTAG + ',' LIKE '%,' + a.AssetTAG + ',%'

2. use a string splitting UDF and then join
SELECT
FROM
(
SELECT f.Val
FROM tableB b
CROSS APPLY dbo.ParseValues(b.AssetTAG,',') f
)m
INNER JOIN TableA a
ON a.AssetTAG = m.Val


ParseValues can be found in below link

http://visakhm.blogspot.in/2010/02/parsing-delimited-string.html