@Fabian ****************
I always insist on learning the script right from the start. Learning to speak Thai with a transcription system is a complete waste of time.
And with a hearing problem, this is even more important.
No matter how bad one's pronounciation is. When you type a word, it is absolutely clear.
No matter how bad one's hearing is, you can easily see what is printed.
Even if you can't hear the difference in tone, there is a clear difference in spelling.
Reading and typing is a huge part of communucation anyway.
I follow Thai language face book groups, read Thai language articles.
I've had to read Thai language contracts, my line communication with all my Thai friends is exclusively in Thai, the line group chat of co-owners is completely in Thai, when I sold a condo my communication with the agent through line was completely in Thai, contract / agreements in Thai etc...
In daily life hearing/speaking situations, the other person's pronounciation is extremely important. Some people (even my brother) are so difficult to understand for me regardless of language) and some I can very easily understand. But a typed word is the same for everybody.
So being bad of hearing doesn't make a difference in the number 1 rule of learning Thai (and most languages) : start with the script from day 1.
Knowing the script helps a lot in understanding what the pronounciation should be anyway, which in turn helps in speaking and understanding.
I have bad hearing, but I have to correct a farang friend all the time because his Thai is extremely limited, and doesn't hear the little nuances in speech like I do, though I have way worse hearing.