You don't have to listen to authentic Thai for very long to realize that comparatively few words are pronounced with the dictionary tone.
All the learning material out there seems to be focused on helping people produce individual words with the supposedly correct tone - but this is only half the picture as I now see things. You also need to understand how the tone system works at sentence level. So far, I have not found anything on this.
What I've noticed myself is that while many syllables are not given their dictionary tone, this doesn't mean that they default to mid/neutral tone, or that their tone is arbitrary. The overall system seems to be that some words have greater weight within the sentence, that those words are given their dictionary tone, and that the tones of the intervening words - I've been calling them interstitial tones for now - are mainly a matter of setting up or recovering from the tonal gestures required by the heavier words.
Obviously, if that's right, it's important to know which are the heavier words.
I am sure this subject must have been investigated before and was wondering:
Whether there is something better than 'interstitial tones' that I could use as search term;
How much of a parallel there is between a word being given its dictionary tone in Thai and a word being stressed in English.