Gatherings of more than 500 people must provide officials with information on the purpose of the event plus Covid-Free Setting measures.
Religious activities should follow guidelines of the religious leader in charge, said authorities.
Measures for the Songkran festival in Chiang Mai have been divided into three phases: before, during, and after the holiday.
Under the first phase, every participant at Songkran events must be fully vaccinated or present a negative antigen test (ATK) taken within the previous 72 hours.
Event organisers should register at the Thai Stop Covid Plus website to evaluate their Covid Free Setting measures.
Under the second phase, permitted activities include pouring water on Buddha images or the hands of seniors, traditional rituals, cultural performances, parades, and concerts.
However, water battles, smearing powder, foam parties, and drinking or selling alcohol are banned.
Visitors will be screened and registered as they enter events while numbers will be limited to prevent overcrowding and ensure distancing of four metres between each person.
Under the third phase, participants should monitor their symptoms for seven days after Songkran and test themselves with an ATK immediately if they develop any Covid symptoms. They should avoid meeting other people in the monitoring period.