In this work, bio-based bisphenol (TP) was synthesized from thymol and 4-phenoxybenzaldehyde. On utilizing TP, structurally different benzoxazines were synthesized using four different amines namely furfurylamine (ff), p-aminophenol (pa), tyramine (ty) and p-toluidine (pt) through Mannich condensation. The molecular structure of developed benzoxazines was confirmed by various spectroscopic analyzes. Among the benzoxazine monomers, TP-pa exhibited the lowest curing temperature of 213°C. TP-pt showed highest antimicrobial activity with maximum inhibition zones of 17 mm for E. coli and 25 mm for S. aureus. Thermal analysis revealed that poly(TP-ty) showed highest thermal stability with char yield of 46% at 850°C, limiting oxygen index value of 35 and heat resistance index up to 208°C. Among the polybenzoxazines, poly(TP-ty) exhibited the highest water contact angle (WCA) value of 146°. All the polybenzoxazines coated over MS specimen demonstrated corrosion inhibition efficiency of 99%, which further validated by density functional theory (DFT) studies. Flexural test revealed that a maximum flexural stress of 1.62 MPa and modulus of 451.69 MPa for thermally cured material.