That a guilty plea can waive a trial and that a timely guilty plea can reduce sentences are among the longest established practices in Thailand's criminal procedure. However, a comprehensive and critical review of Thailand's law and practices on dealing with guilty pleas seems to be long overdue. This article fills this gap in the literature by comparing Thai law and practices on the issue with those of England and the US and pointing out five main areas of Thailand's law and practices that need to be reconsidered: procedural effects of guilty pleas, conditions of a valid guilty plea, the significance of lawyers in advising their clients to plead guilty, a reduction of sentences for guilty pleas and the right of appeal and the right to reopen criminal cases for defendants who plead guilty.