Sure you can do it. It's not that important how good your memory is, but how much time you spend learning and how focused you are.
For Thai, in my opinion:
Get some classes with a teacher (not just a native speaker. A teacher will be able to teach you right pronunciation. My suggestion is this:
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(they have a youtube channel about learning Thai).
Subscribe to Pimsleur- great for beginners (but don't start with only this)
The best book to teach you writing I think is Write in Thai in 4 weeks, just obviously you won't learn it in 4 months even, but you can understand the most important things. It is not that difficult in general.
Just don't listen to people who would tell you that you will learn Thai the best on Sukhumvit in a bar or when sleeping. Those people just look for excuses.
Also Pamboon Thai for beginners is good although a bit old fashioned, as you can listen to the dialogues that are in the book.
Good luck!