I have a few Thai friends who don't speak English or Spanish but would like to try one. Which do you think would be easier to grasp. Anything from pronunciation to grammar I mean. Are there any Thai people who have tried one or both?
Also, any tips for teaching english or spanish to Thai people?

u should teach them how to pronounce in english..............spanish may be easier coz believe it or not i can speak and understand spanish well eventhough i didnt learn it at school and dont talk it at home...........but i do read and listen to spanish song.....and watch their programmes

I'm a native spanish speaker and I'm also learning english. I can say that english is much easier in some ways, for ex the verbs are similar in I, you, we, and they. but in spanish each person has a different verb for ex: yo tengo, tu tienes, get it? :) anyway I think spanish is easier to pronounce.

Believe it or not English is the hardest language to learn. If your looking for the easier of the two I'd say Spanish.

I am Thai. The second languagues i chose to learn despite English were German ,then Spanish.
Spanish is the easiest one, both its grammar and accent. My friends who learn them both (English and Spanish) agree with me too.

p.s. I think you should teach how to pronounce alphabets and words correctly, I found it improves listening skill very well. Urge them to watch soundtrack movies because they are very good tools to learn launguage and entertaining as well.

One of my Thai friends learned spanish first, she got hold of it in like 1 year. (She lived in Spain for 2 years) Her english is not very good though but it's understanable.

I would have to say Spanish because its easier to pronounce and sentence structure is far more easier than English. A good way to learn a language though is to listen to music and watch movies in that language to grasp better understanding and pronunciation.