Here are some popular events and festivals in Thailand by month:

January:

- Thai New Year (Songkran) - celebrated nationwide with water fights and traditional ceremonies

- Bo Sang Umbrella Festival in Chiang Mai - showcasing beautifully handcrafted umbrellas and parasols

February:

- Chiang Mai Flower Festival - featuring colorful parades, floral displays, and beauty pageants

- Makha Bucha Day - a Buddhist holiday commemorating the teachings of Buddha

March:

- Hua Hin International Kite Festival - showcasing intricate kites of various shapes and sizes

- Chak Phra Festival in Southern Thailand - marking the end of Buddhist Lent with boat races and parades

April:

- Thai New Year (Songkran) - festivities continue into April, especially in Chiang Mai and Bangkok

- Bangkok International Film Festival - showcasing local and international films

May:

- Visakha Bucha Day - celebrating the birth, enlightenment, and passing of Buddha

- Rocket Festival in Isan - featuring traditional rocket launching competitions

June:

- Phi Ta Khon Festival in Loei - a colorful ghost festival with masked processions and traditional dances

- Candle Festival in Ubon Ratchathani - elaborate candle-lit processions and artistic displays

July:

- Asanha Bucha Day - commemorating Buddha's first sermon

- Khao Phansa (Buddhist Lent) - monks begin a period of meditation and retreat

August:

- Queen Sirikit's Birthday - honoring the Queen Mother with various ceremonies and events

- Phuket Vegetarian Festival - featuring street processions, rituals, and purifying ceremonies

September:

- Por Tor Festival in Phuket - a traditional Chinese festival honoring ancestors with offerings and ceremonies

- Hae Krathup Tradition in Nakhon Si Thammarat - a unique ritual involving the floating of decorated banana leaf boats

October:

- Rup Khao Phansa (End of Buddhist Lent) - marking the end of the rainy season retreat for monks

- Vegetarian Festival in Phuket - participants observe a strict vegetarian diet and engage in rituals for purification and merit-making

November:

- Loy Krathong Festival - celebrated nationwide with floating decorated banana leaf boats on rivers and lakes

- Elephant Roundup in Surin - showcasing elephant shows, parades, and traditional elephant-related activities

December:

- King's Birthday (Father's Day) - honoring the late King Bhumibol Adulyadej

- Christmas and New Year celebrations - especially in tourist areas and major cities with festive decorations and events

Please note that event dates may vary each year, so it's advisable to check the specific dates and details closer to your travel time.