The second largest city of the country, Nakhon Ratchasima has a population of 190 thousands and the third largest city Chiang Mai, 170 thousands and there is no other big local city. This means a single high concentration in Bangkok.
If we take a look at the cities along the northern line which is the objective of this study, those with population over 100 thousands are only two, namely Chiang Mai and Nakhon Sawan, followed by Phitsanulok (nearly 100 thousands) and some others (mostly approx. 40 to 50 thousands).
In the Bangkok metropolitan region including adjacent 5 prefectures, the total population ratio showed a peak in 1989 (15.6 % of the total) but it fell down to as low as 15.1 % in 1993 showing a gradual development of the rural areas.
(3) Climate
Thailand is located in the northern hemispheric tropical zone and each year is divided into rainy and dry seasons. The dry season is further divided into cool and hot seasons. The rainy season typically starts in mid May and ends in around November every year. March through May is the hottest season and the temperature in Bangkok goes up to as near as 40℃. The cool season lasts from November through February when the temperature generally comes down nation-wide and Bangkok may experience 15℃ or so at night. (See the following table.)
