Will seborrheic dermatitis cause thinner hairs by clogging the pores?

This needs an in-person evaluation.  I recommend getting a formal evaluation with a hair loss expert to go over your condition and advise you on best treatment options. There are great non-invasive options like prp/progesterone and/or hair transplantation. See an expert. Best, Dr. Emer

Actually most of the patients suffer from hair loss complain about oily skin, scalp and hair.  That leads to them think about oily skin causes hair loss. But it is not true . there is no relation between hair loss and oily  skin .

Seborrheic dermatitis (seb derm) is probably not the reason for your thinner hairs. Please review with your physicians whether androgenetic alopecia is a more likely diagnosis and contributor.