I just want to make a small correction. The late Kru Tonglor of muay chaiya taught the knife to several of his top students as an extension of their training. I learned it from one of his top students, saw it trained with another top instructor as well as now see it with kru praeng. Kru praeng has invented endless variations to muay chaiya so he does whatever he does and calls it whatever he does, he has created his own thing, so I refrain from commenting on that. Some learned it and some didnt and I am sure in this current atmosphere its probably a huge point of contention. The muay chaiya guys used a very specific blade which they said kru tong really liked which is like a mini kukri. I love the kukri so i adapted to the training very well.
In muay korat, they sometimes put a knife in to show you the extension of the training for more practical purposes. Old style muay was more of a complete martial art beyond just the bare knuckle fighting. But for the most part, the knife is not overly taught or stressed. But knife defense is covered in the self defense portions in most systems.
I have trained extensively in the knife throughout se asia as it is one of my specialities.
Most krabi krabong schools have the knife as part of their curriculum, some more, some less, some not at all, depends on the school and teacher, there is not one school but many different schools. Some are more practical, some are less. Depends on the teacher and school. You will see less in a physical education type of krabi krabong program because of safety and not advocating violence(thus more self defense against it) and more in the combative programs(extensive knife training progression, attack and defense). Knife throwing also taught by most.
The most practical of the knife is in the military programs and with the older teachers who were part of the seri thai(free thai movement) which was an underground resistence movement against the japanese occupation during world war II. Some krabi krabong teachers took part and they trained together in more practical techniques to be used against the japanese on the ground. I learned from two and they have many quick dispatch techniques and train in a concise practical manner. But they don't teach in the open and dont advertise it.
We see many good techniques born from this type of thing as well in Burma with the OSS and other forces, training and assimilating techniques for the native people fighting against the occupiers. After training with some top military officiers in Burma, I actually was given a burmese military training manual, it was filled with knife fighting techniques, so they are definitely covered in the military as well as in thiang.
Learned some decent knife techniques from an old cambodian in cambodia as well. So its there too in various forms.
Again like we talked about in the krabi krabong threads, you have to understand the different training modalities to find what you are looking for.