Sorry if this has already been answered but i was unable to find using search. I have traveled to spain with my thai gf on 2 occasions, first time she got a 2 week visa then the second a 3 month one. Can anyone tell me what would be the maxium time we can apply for for a visa for her? Also if it was a multi entry visa, does it mean she needs to go back to thai then back to spain or is there somewere closer she could say daytrip to?

You can get a visa valid for 6months, 1year or 2 year but AFAIK the maximum time a tourist can stay in the Schengen states on a short stay type C multi entry visa (whether it is valid for 6 months, 1 year or 2 years) is 90 days in 180 days.

That is once she has spent a total of 90 days in the Schengen states she cannot re-enter until after 180 days has elapsed since her first entry(assuming the multi visa is still valid). If multi entry she can enter and exit as many times as she wishes until she reaches 90days.

She can, of course, leave the Schengen states for anywhere (to sit out the 90days) provided she has permission to enter that country that is outside the Schengen area.