Here's an easy explanation. Thainess is similar to Englishness ???? On a serious note, I was once asked by the head of English department in one of public high schools to translate a text and there was a word Thainess "Kwam Pen Thai" (ความเป็นไทย). Instead of Thainess I translated it to Thai culture, traditions and values. I explained to my boss that Thainess was invented by someone Thai and could not be used in the same meaning with other nationalities. Though, I don't know what happened to may translation ????