Songkran is Thailand’s New Year festival which falls on the 13th, 14th & 15th of April in Thailand but will be celebrated on the 25th & 26th in Yoyogi park. In Thailand it marks the beginning of the rainy season and is mostly celebrated with boisterous water fights. There’s a strong chance it will be somewhat more restrained in Japan but expect food, drink and music to be available.
Songkran will be celebrated again in Golden Week on the 3rd and 4th of May in Nerima’s Hikarigaoka park.
To prevent the spread of COVID-19, many events have been canceled. Always check official sites before heading to an event.