April 22 Songkran Festival (observed) Thai New Year.
10-12 AM: Chanting, Dhamma talk, monk alms round, food offering to monks, blessing from monks, laity lunch.
12:30-3:00 PM: Transfer merits to the deceased, offering requisites ceremony, Asian youth classical dancing, gratitude ceremony, respect to the elders, sand pagoda ceremony, ending.
May 27 Vidakha Puja (observed)
Visakha Puja celebrates the Buddha’s birthday, enlightenment day, and passing away day. They all occurred in his life on the same full-moon day in May. Therefore, this is one of the most important days in the Buddhist tradition, if not the most important. Visakha refers to the Visakha asterism, a Vedic construct, having to do with the day when the moon and the Visakha constellation align.
Ajahn Lee spoke about the way Thais honor this day: https://www.accesstoinsight.org/lib/thai/lee/visakha.html