It’s also a common rite of passage for young men to serve as a monk for a short time.
Thais believe that when a man turns 20, he should be ordained and enter a monastery for a period of time to study dharma, the teachings of the Lord Buddha.
The chaotic lifestyle of today does not allow people to leave the worldly life behind for three months. The tradition has therefore changed. The monkhood period is shortened and varies from one week to 15 days or one month, depending on the time the person has available.
It’s also a common rite of passage for young men to serve as a monk for a short time.
https://www.thailandfoundation.or.th/culture_heritage/buat-nak-rituals-before-monkhood/