The current politial situation in Thailand can only be understood in its historical context. The Western notion expressed by some that "the coup was justified to fight corruption of the toppled regime" is quite simplistic, legalistic and seen from a purely Western perspective. For more profound backround information, two articles stand out: Kasian Tejapira's Toppling Thaksin (PDF download is at the bottom of the page) and Duncan McCargo's **Network monarchy and legitimacy crises in Thailand** (free download after registration). Both articles were written before the coup, outlining the conficts of power which led to the putsch of September 19th.
Freethai: How to register in order to get the free pdf of Network monarchy and legitimacy crises in Thailand ?
dirk: @Freethai: The "register and get the free excerpt" might have been a temporary promotion; currently the article seems to be available only in exchange for payment. The link also changed from taylorandfrancis to informaworld, which might point to some corporate reorganization in the meantime. Not sure if you can find other sources for this article on the web. Good luck!