Thais had used a lunar calendar since 1249 (1792 BE) in the Sukhothai Kingdom. We counted the first day of the first waning moon (during November to January) as New Year’s day.
At that time, people followed the Shalivahana era or the Saka era: มหาศักราช, in order to calculate a year. Shalivahana was a legendary emperor of ancient India, ruling from Pratishathana or Paithan, presently Maharashtra.
Later Thais accepted the Hindu belief of Brahmins. The 1st of the fifth waxing moon became the New Year which was originally consistent with Songkran for Thais (following the lunar calender). That’s why we called Songkran as the Thai New Year.
After 1569 (2112 BE) during Ayutthaya Kingdom’s reign, Chulasakarat: จุลศักราช was used officially in Thailand until 1888 (2431 BE); however, the first year of Chulasakarat started in 638 (1181 BE). It is a lunisolar calendar derived from the Burmese calendar.
King Chulalongkorn (Rama V) adopted the Thai solar calendar as the Siamese version of the Gregorian calendar in 1888 as the legal calendar replacing the Thai lunar calendar.
He also decreed a change in vulgar reckoning to the Rattanakosin Era or Rattanakosin Sok: รัตนโกสินทร์ศก. Its first year began on 6th April 1782 when King Buddhayotfa (Rama I), the founder of the Chakri Dynasty, laid the foundation of Bangkok as a capital.
Before, New Year coincided with the date calculated for Songkran, when the Sun transits the constellation of Aries, the first astrological sign in the Zodiac. King Chulalongkorn decreed the first of April to be the New Year’s Day in the year following the adoption of the solar calendar.
After using Rattanakosin Sok for 24 years, Buddhist Era (abbreviation BE), พุทธศักราช was decreed officially in 1913 (2456 BE). What’s more, on 6 September 1940, Prime Minister Plaek Pibulsongkram announced the 1st of January 1941 (2484 BE) to be the official New Year from then on.
Nowadays, the Common Era New Year’s Day (1 January) and Songkran (13 – 15 April), the Thai traditional New Year, are important public holidays in Thailand.
For Thais, we will say สวัสดีปีใหม่ /sà-wàd-dee bpee mài/ to each other on New Year’s Day. I wish you a prosperous and healthy year!
sà-wàd-dee bpee mài kà