There is a lot more to this film than immediately meets the eye. Most Thai historicals or ghost stories are loaded with anachronistic pop culture cliches. This one wasn't; people spoke with their mouths filled with betel (maak), the lead actress didn't have lipstick, the houses were quite realistic, etc. In addition, the rural monks switched between high-level speech and country slang. The point is that this film is a serious attempt to do justice to both the original tale and the time period it is set in.
The empathy for Nak far surpassed the scariness. What stood out for me is that Nak's justification for her actions seemed quite defensible, adding to the anguished poignancy of the situation.
Asian ghost stories, when done well, have a strongly moral character. This is one of the finest examples I have seen.