During his reign, the pressure of Western expansionism was felt for the first time in Siam. Mongkut embraced Western innovations and initiated the modernization of Siam, both in technology and culture—earning him the nickname "The Father of Science and Technology" in Siam.
Mongkut was also known for his appointing his brother, Prince Chutamani, as Second King, crowned in 1851 as King Pinklao. Mongkut himself assured the country that Pinklao should be respected with equal honor to himself. Mongkut's reign was also the time when the power of the House of Bunnag reached its zenith and became the most powerful noble family of Siam.