Never Forget Your Enemy

From the synopsis, both series have enemies to lovers vibes.
Both are BLs. Both are from Thailand though Never Forget Your Enemy is made up of Korean cast.

Both MCs forget their past including that they are in a relationship. The MLs try to make the other remember or fall in love with them again.

The similarity in both Never Forget Your Enemy and Secret Lover is that the main couples are childhood friends that turn to lovers. Also, one of the boys secretly keeps girls from approaching his friend by dating them. It started as a requited love then they became boyfriends in their later years after high school.