combine two select queries?
Thanks Lennart!
A second sub select query within the first worked.

select TTS.SSML, TTS_TAG.SORTID, TTS.VoiceId , TTS_TAG.TAGID, 
(select max(TTS_TAG.SORTID) from TTS_TAG
where TTS_TAG.TAGID = 1) as maxsort
FROM TTS 
left join TTS_TAG
on TTS_TAG.TTSID = TTS.TTSID 
where TTS.MID = 15