March 3rd - Makha Bucha Day

April 6th - Chakri Memorial Day

April 13th, 14th and 15th - Songkran Festival (Festival runs until April 19 in Pattaya)

May 1st - National Labour Day

May 5th - Coronation Day

May 10th - Royal Ploughing Ceremony Day

May 31st - Visakha Bucha Day

July 29th - Asarnha Bucha Day

July 30th - Buddhist Lent Day

August 12th - H.M. The Queen's Birthday

October - Chulalongkorn Memorial Day

December 5th - H.M. The King's Birthday

December 10th - Constitution Day

December 31st - New Year's Eve

Do the Thai's have big party's on these days?
I ask as I will be there 5th May (Coronation day) and as they love their Royal Family so much I would imagine they have quite a spectacular time.
Also
Anyone know what the Royal Ploughing day is all about?

Great question and here is what I found on the internet at: Royal Plowing Ceremony

The rice planting season usually begins in April or May with the annual Royal Ploughing Ceremony in Bangkok, presided over by His Majesty the King. This ceremony, designed to give an auspicious beginning to the new planting season, originally was a pure Brahmanic rite. During the reign of King Rama IV some Buddhist elements were added to it. Schoolchildren are on holiday during this, the hottest time of the year and, countrywide, farm labor braces for the gargantuan effort of hand-planting rice in a way that would have been familiar to their ancestors, and their ancestors before them.
The Annual First Ploughing Ceremony which is an ancient Brahminic rite to ensure a good harvest due to an abundance of rain and an absence of pestilence and floods was revived by the Government, in the year B.E. 2503 (A.D. 1960), in accordance with His Majesty the King's wish to give importance to a day dedicated to farmers throughout the Kingdom. The grains sown on the Ceremonial Field at the Sanam Luang Grounds since the year B.E. 2505 (A.D. 1962) have been rice seeds from the Chitralada Farm's experimental rice fields in the grounds of Chitralada Villa, Dusit Palace, Bangkok, Thailand.
His Majesty the King initiated the Chitralada Farm's Rice Cultivation Project in the grounds of Chitralada Villa, Dusit Palace, in order to conduct experiments in rice cultivation and crop rotation whereby data could be collected in order for His Majesty to analyze before devising ways and means to help raise the standard of living of the Thai people, the majority of whom are farmers. The project commenced on July 16th. B.E. 2504 (A.D. 1961) when His Majesty sowed rice seeds in the experimental rice plots. His Majesty the King personally designated varying formulae in the usage of chemical and organic fertilizers and witnessed the various stages of rice farming from seedling to harvesting and threshing.
The Annual Ploughing Ceremony is also an occasion when His Majesty the King graciously presents awards and certificates to outstanding farmers from each region, whose fields produced the highest yields during the previous year. Upon completion of the ceremony, farmers from all parts of the Kingdom try to obtain some seeds, which had previously been sown, in order to mix with their own grains as portending good omen when scattered in their own fields.
Before the Annual Ploughing Ceremony one day, thursday May 8, 1997, His Majesty the King pours lustral water on the forehead of Permanent Secretary for Agriculture and Cooperatives Taweesakdi Sesawech in his capacity as Phraya Raekna, Lord of the Ploughing Ceremony, during a preparation ceremony involving gold and silver pails held at the Temple of the Emerald Buddha in the Grand Palace. Phraya Raekna, with the assistance of four celestial maidens and a pair of sacred oxen, will lead the annual traditional Ploughing Ceremony at Sanam Luang this morning, Friday May 9, 1997, to mark the beginning of the rice-planting season. His Majesty will preside over the ceremony, present awards to last year's outstanding farmers and distribute rice seeds fro the experimental crop station in the grounds of Chitralada Villa, Dusit Palace as a gift to farmers throughout the country.
The ceremony began at 8.30 a.m. on May 9, 1997 and was presided over by His Majesty the King, who was accompanied by HRH Crown Prince Maha Vajiralongkorn and HRH Princess Maha Chakri Sirindhorn.
Before the ceremony, Phraya Raekna chose a four-keup-long (one metre) panung cloth out of tree pieces --- four-kueb-long, five-kueb-long and six-kueb-long items. From the length of the cloth chosen by the Phraya Raekna, it was predicted that there would be plenty of water this year, highland rice crops would be bountiful while lowland rice crops would sustain some damage.
During the ceremony, the oxen, Rung and Roj, were given grass, rice, corn, beans, sesame, liquor and water to choose from. They chose corn and water and thus it was predicted that there would be abundant crops, vegetables, rice and other agricultural products this year. The Ploughing Ceremony is held to mark the beginning of the planting season.

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I logged onto my Yahoo account today and there was a picture of the Pii Tha Khon festival and a blurb about it with a link to the NY Times Travel section on Thailand. There it explained the festival, when , where, why and also discussed the Ploughing day festival. I think the title of the article was Thailand keeps the fest in festival. Very good pictures of Pii Khon. I will definitely go to Pii Tha Khon sometime when I am in country when it happens.