Relax in body and mind..
Whether the Thai language is difficult or easy to learn is hard to say, and there are probably many opinions about that topic, but people with "language-ear" it should not be that difficult to learn to do well in Thai after a little in-depth studies of language composition.
It is so that the Thai language has quite strict rules with regards to grammar, as many sentences in European languages, translated into Thai, will be handled with far fewer words in Thai.
The hardest thing about the thai language is probably the "tonalities” which means that it, in principle (for not trained ears) it might sound like the same or similar words actually mean many different things depending on how the pressure down.
Keep the focus on the tonality
We talk about that there are 5 keys which are distributed as follows: medium, high, low, rising and falling tone, and if you're not careful, you can easily get to say something completely different than what you had originally imagined. Remember, however, that smiles and laughter is a very common part of the Thai way of way of communicating, so you come to grief so that together you are guaranteed with a smile or a laugh, and you have no reason to be embarrassed :-)
Thais can namely really like if you as a tourist in the country trying you with the Thai language and learn the most common words and phrases.
On this page you can see some of the most used words and expressions, which you can usefully try to learn before the journey goes to Thailand.