今日 は ありがとう Note the long pronunciation of the "o"s. They result from yo/よ + u/う and to/と + u/う in this case. — Tae Kim's Japanese Grammar flashcard

As for today - thank you (or less literal: Thank you for today). kyou: today "ha" marks "kyou" as the topic you're talking about. Imagine someone did something big for you today. Just saying "thank you" may not make clear what you're thanking for, so adding "kyou ha" makes sense here. It points out that you're thanking for what happened throughout the day. "ha" (always spelled in Hiragana: は) is the "topic particle" and is always pronounced "wa". It's attached to a noun and identifies it as the topic of what you're talking about or as topic of the sentence. It's very important to keep in mind the entire "xxx ha..." is usually omitted, if the topic is clear from context.