Should the Masbooq read thana when he joins salah or when recitation has started?
In the name of Allah, the most Beneficent, the most Merciful.
The masbooq should not read thana when he joins the salah and similarly when he joins such salah where the Imam has started his recitation whether it is loud salah or quiet salah. (Fatawa Darul Uloom Deoband p.392 v.3)
Only Allah Knows Best
Mohammed Tosir Miah
Darul Ifta Birmingham.