dear jonathan,
i have written a very long email! in case you have limited time, i am writing a summary of what is below. yes, please do give the seasite dialogues another try. the reading sections with accompanying audio are excellent. they speak slowly so you can hear the nuances in the letters. as for dialects, i am familiar with the spoken variants, but i have not seen a printed or web resource which you would call a "study" of the subject. as to "sanskrit," it came as a great surprise to me after two years of intensive volunteer work, and a sudden wealth of free time for study, that khmer letters are more accurately described as "modern sanskrit." the devanagari script, which i used to learn sanskrit, is much younger than the grantha-pallava script which was adapted by people of se asia perhaps before -200 ce, depending on your bibliography. there are 10 or 12 letters in modern khmer that are exactly the same as their 2000 year old antecedents! this is a real treasure for me personally. i can still read devanagari, but i have nearly lost interest in it. ok, that's the intro. if you have time for more reading, here is my story:
i must say i am impressed with your achievement in this study! my answers to your questions are mostly the result of my own observations and experience, rather than the consensus of scholarship.
i learned to speak and read khmer because i lived in a village where no one could speak english. my students were all from a fake orphanage which i dismantled by sharing the financial info to each contributor. each was told that he or she was the "only sponsor." all the kids had parents who loaned them to the fake orphanage in return for a percentage of the donations. after the fake school-orphanage closed i started a small school in the village with the parents' approval. the kids refused to study english, so i learned khmer instead. that's my history.
after that project ended, i found free time to look at the temple inscriptions. it turned out there was one small temple 100 years older than angkor wat behind my house!!! khmer people told me that these were sanskrit, but i did not believe them at first because i had learned sanskrit via devanagari script. the modern khmer script derives from the grantha-pallava scripts, and ultimately from the brahmi. so i was very pleasantly surprised to learn that the khmer letters i had learned were actually a much older form of sanskrit which arrived on the mekong delta perhaps as early as -200 bce with indian merchants.
the date of this migration of indian merchants to the mekong is still debatable. the earliest stone inscriptions containing letters identifiable with modern khmer letters so far discovered are dated around 500 ce. at that time, three hundred years before the beginning of the "Great khmer empire (jayavarman and kulen mountain)" the people of this region had no written language. the arrival of the educated indian merchants apparently satisfied a hunger for writing which must pervade an intelligent person who can speak but cannot record his or her ideas. it caught like fire.
the problem is that most writing was done with material which was destroyed even by rain according to a chinese diplomat who visited angkor around the end of the 13th century. so we are left with these stone inscriptions, some of which i have photographed and read myself. they are interesting but also disappointing. they contain lists of the names of the gods the temple was dedicated to, the wealth given to the temple, and in most cases, the inscriptions are about 25% of the total a list of the names of slaves given to operate the fields and do the maintenance of the temple and grounds. not very inspiring.
but! what is exciting is that if you have learned to read modern khmer, and if you know some sanskrit, you can read the inscriptions! you can see that many of the letters are the same today as they were 2000 years ago! this is amazing to me.
now to your question about dialects. linguistics scholars in cambodia are sadly beholden to the misconception that these words come from pali. the reason is that the prayers chanted by monks here are from the pali canon of theravada buddhism called the "tipitaka." in fact, ordinary camobian people will look at a word and declare that it is "baley" (meaning pali.) all of this confusion is the result of a sad coincidence of history.
the khmer rouge intended to destroy khmer culture. this included destroying religion and education, both of which occurred at the wats or pagodas. monks were killed along with all other educated people. today, as a result, khmer people are unaware that their form of buddhism comes from sri lanka. starting before suryvarman I, the kings oscillated from brahmanism to buddhism and back. one king supposedly destroyed 10000 sculptures of the buddha!
so, the situation here today is this. khmer people are polytheistic. this is central to understanding the dialects spoken here. people of different religious beliefs segregate as you know, but in cambodia it is off the charts. most people do rituals to three religions: theravada buddhism, a remnant of brahmanism, and a deviant of confucianism. when christians "convert" khmer people, they do not realize that khmer people have just added a 4th religion to their collection.
back to the point of dialects. spoken khmer is very different from the khmer i read in books. and usually when i point to a word and ask for help my friend does not know the word. this is because of a pretentious attempt by authors to appear "scholarly." they use a lot of words of sanskrit (not pali) origin, and regular people cannot understand the words. on the other hand, very few books are written the way people speak! in spite of the dialectal variation, the same textbooks are used in all high schools throughout cambodia. if you are able to find a printed resource such as a "survey of spoken dialects" in cambodia it would be extremely rare and i would be very interested to see it.
we all know the dialectical variations and people make fun of each other here, perhaps as bavarians in germany, and the swiss dialects of german. but for a study of the dialects, that is really pushing the limit for cambodian people, who are still mostly illiterate.
in my village, when my kids refused to learn english, and i found some 7th year high school students who could not read khmer, we abandoned english and focused on reading khmer books. but now there is this glamorous trend at the universities here to use english textbooks which the students cannot read! it is all maddening if you do not have a sense of humor.
i have a lot of very funny stories if you do have a sense of humor. but the tragedy of the genocide has a long shadow, and the current prime minister of 30 years was a member of the khmer rouge. people are afraid of him. many people still pretend that they have no education. it is very hard to get answers, even in remote places where there is no apparent danger. there is still the fear that "big brother" has eyes everywhere!
to tie up one loose end, the origin of all the dialects in this region derives from the common grantha-pallava origin. thai, vietnamese, malay, javanese, khmer, lao, all are derived from the same root. khmer people hate vietnamese people because they do not know the history that the vietnamese army defeated the khmer rouge and stopped the genocide. khmer people do not know that vietnamese families sent rice to khmer families, and when i tell them they do not believe me! these are all the horrible shadow of the genocide. if you want to observe a "stone age culture" with ipads and smartphones, just live in cambodia for a few years. so many stories to tell...
in the picture below the hilighted words "srok khmer" are clearly similar to their modern equivalent forms. few people agree with me on this because the lion's share of the text is a hodgepodge of old hindu names, place names that are no longer used, and so forth. when i point to the word "water buffalo" with excitement and say, "see, that is the same word you use today. same as 2000 years ago..." peeps are underwhelmed.
mark