Complex sentence: Sarit's "revolution" brought an intense crackdown on "leftists"; however, as genuine communists were rare in Thailand, it was the mildly socialist or neutralist professors, politicians and newspapers which bore the brunt of the suppression.
Split into simpler sentences: Sarit's "revolution" brought an intense crackdown on "leftists". As genuine communists were rare in Thailand, it was the mildly socialist or neutralist professors, politicians, and newspapers which bore the brunt of the suppression.