When Bangkok was named the capital of Siam it held an inconsiderable population of some fifty thousand. Now, two hundred years later, this capital city boasts some five million residents. A prodigious population increase, indeed: a hundredfold gain generated by an ever-increasing rate of growth, which, after gathering momentum only gradually during the greater part of the nineteenth century, rose rapidly around the turn of this century and has since soared. The foregoing compendious description is shown on Figure I as the curve which charts the march of the population of the built-up area of the city. I have calculated this particular population by reworking the numbers reported at particular times by certain “eyewitnesses”. Since the turn of this century, the “eyewitnesses” have been censuses and registration counts for administrative areas; earlier “witnesses” are the postal census of 1882 and the considered estimate of the population of the city proper in 1822 by the “very trustworthy” Dr John Crawfurd, Head-of-Mission to the Courts of Siam and Cochin China deputised by the Governor-General of India. I have forsaken all the many other pre-twentieth century eyewitness estimates of the population of Bangkok. Why?