Sentence:  Thais have been watching for signs of <WSD>friction</WSD> between the armed forces and the monarchy—the country's two biggest sources of political power—since the death in October of Bhumibol Adulyadej, King Vajiralongkorn's long-reigning father. 
Meaning of the word marked with <WSD> tags:  Conflict, as between persons having dissimilar ideas or interests; clash.