SIAM'S OLD LUNAR CALENDER
In the days prior to the formation of the first Thai kingdom of Siam, in central Thailand, that rich agricultural area was ruled and managed first by the Mon Dvaravati Kingdom (5th to 9th centuries) and then by the Khmer Angkor Kingdom (10th to 12th centuries). The Mons and the Khmers were both highly skilled agriculturalists and developed advanced irrigation and rice farming systems by making use of the Chao Phraya River. When the Tais assumed control of the area in the 13th century, they adopted the Mon-Khmer systems. This highly skilled agricultural culture, which became strongly attached to Buddhism, was a society based almost entirely on these two features, and that combination has been passed on to many Thai countryside areas of today.
Again referring Months of the Thai Lunar Calendar, we see that in the old calendar, which was based on the growing seasons, the first lunar month occurred sometime between late November and early December. From this we can assume that at that time either weather patterns were quite different from those of today or the peoples of old designated the New Year as the time of the rice harvest rather than a new growing season. Today in many of the rural villages of Thailand, farmers continue to celebrate their New Year according to the old calendar, that is, at the end of November, despite the fact that the New Year is now in April, which is in the 5th lunar month of the old calendar.
Phases of the Moon and Date & Day, according to the old lunar calendar -- shows how the old lunar dates for Thai New Year are reconciled with the contemporary western calendar dates. The first two days together make up what is called the 'Troot Festival', where 'Troot' has a double meaning :'the end of something combined with the beginning of something new'. The larger Songkran Festival as it is celebrated today is comprised of four days. The first two are the 'Troot Festival', and the second two immediately follow and are a time for relaxation and merriment after attending to family and religious duties.