So when I graduated almost 2 years ago I had a very high level of Thai. Since then I have started learning Spanish and have been living in Spanish speaking countries for the past 9 months and I haven't really had a chance to practice my Thai. I was wondering if any you guys had ideas on how to maintain language ability whilst learning another language?

Thanks for your help! 

If you want to keep up to date on vocab and grammar and such, either find a book in that language or better yet, find a online newspaper in that language(s), so then you can get it practice anytime you need.  And if you don't know a word, just look it up.  Using articles is a well known practice for learning and reading common usage words and learning new ones amongst language learners, and it doesn't require the same commitment as a book or any literature.  You can also learn about culture this way as well.
Poetry is similar if you want to do the same thing, because they are often short, and you can learn about the writings that have survived for centuries.