Al-jawab billahi at-taufeeq (the answer with Allah's guidance)
Yes, to remove unwanted hair whilst fasting is permissible.
From Hadiths, it is known that it is disliked to leave this till the hair becomes long.
It is recommended that this be done weekly, ideally on Friday (before the Friday prayer). It is not disliked to delay this to two weeks. It is blameworthy beyond that, and sinful beyond 40 days. [Tahtawi, Hashiyat al-Maraqi]
