I purchased Linguaphone’s PDQ Thai (stands for Pretty Darned Quick!) before I came to Thailand 15 years ago and it really helped me get good start on the importance of Thai tones. Their PDQ series is targeted as a quick start on the essentials before you travel on holiday.
With regards to teachers, unless they are very experienced I’ve found many Thai ‘teachers’ don’t understand the nuances around the tones as obviously they don’t learn that way. It’s like most English natives can’t explain grammar. Unfortunately being able to speak fluent English is not enough to be a good Thai teacher, they need additional training in how to teach it as a foreign language.
Here’s a link to the course and it’s still only £30, The same price I paid when I bought it!
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