If you have a chance to visit many temples, you will see that Thai Buddhist guys prefer to be ordained during the Buddhist Lent. When they are monks and the senior monks have to stay in the temples, so the new monks and the senior monks are in the same places, the senior monks will teach what they are expert to the new monks.
Simply, the Buddhist Lent is the Moral Camping period for monks. It is the time for monks to study Pali Cannon because the monks have more time than other periods.