Somdet Chaophraya Borom Maha Sri Suriwongse

The British had been granted trade permissions in the 1826 Burney Treaty but much of traditional royal monopoly was retained. Trade with Westerners had been monopolized by Phra Klang Sinka or Royal Storage Department since 1511. All Western cargoes were monitored by the Phra Klang Sinka who collected tariffs as the source of royal court revenue. The Burney Treaty of 1826 allowed British merchants to trade directly with the local Siamese but they were still subjected to the traditional tariff that measured on the width of the arriving merchant ship and the British residing in Siam were subjected to Siamese laws. After the First Opium War, the British was eager to demand free trade in Siam. James Brooke the governor of Labuan arrived in Bangkok in September 1850. King Rama III elevated Chuang to Phraya Sri Suriyawongse and assigned him to receive Brooke. However, as the king had been ill, no further agreement was reached.

John Bowring the governor of Hong Kong arrived at Bangkok and the Bowring Treaty was signed in April 1855, making a huge impact on the Siamese economy.

Upon the coronation of King Mongkut in April 1851, Prince Isaret Rangsan was made the Vice-King Pinklao at the Front Palace and Chuang's father the Phraklang was made Somdet Chao Phraya Borom Maha Prayurawongse. Chuang was also made Chao Phraya Sri Suriyawongse (Thai: เจ้าพระยาศรีสุริยวงศ์) the deputy Kalahom the Minister of Southern Siam. His father held the position of Samuha Kalahom de jure as Sri Suriyawongse had already taken his father's responsibilities in the Kalahom. Sri Suriyawongse moved to his new residence in Khlong San District, where he maintained a private dock and continued to engage in shipbuilding.

John Bowring arrived in April 1855 and Sri Suriyawongse received him with pomp ceremonies. His father Prayurawongse strongly opposed British proposals on free trade issues but King Mongkut and Sri Suriyawongse had realized that Siam was in no position to resist British demands. The Bowring Treaty was achieved through Sri Suriyawongse's mediation with his father. The traditional ship-width tariff was abolished. The free trade and extraterritoriality was granted to the British and the four hundred years of royal monopoly on Western trade was ended.

Sri Suriyawongse's father Prayurawongse died in April 1855, one month after the Bowring Treaty. Sri Suriyawongse was officially invested as Samuha Kalahom the Prime Minister of Southern Siam and became de facto in charge of Siamese foreign affairs. Sri Suriyawongse was then called by the honorific Pana Hua Chao Than (Thai: พณหัวเจ้าท่าน). Bowring Treaty was the first of "unequal treaties" that had been agreed by Siam with Western nations. The free trades and extraterritoriality was granted to the United States (Harris) in May 1856 and France (Montigny) in August 1856, all of which Sri Suriyawongse and Prince Wongsa Dhiraj Snid played leading roles.

In the reign of King Mongkut, Siam established the first standing navy and was divided into the Royal Navy and the Front Palace Navy. Sri Suriyawongse became the first ever Commander of the Royal Navy while the Front Palace Navy was commanded by Vice-King Pinklao himself. In 1860, King Mongkut ordered Sri Suriyawongse to lead the construction of Phra Nakhon Khiri at Phetchaburi to be a detached palace.

Cambodia had been traditionally under Siamese suzerainty. In August 1863, La Grandière the French admiral had King Norodom of Cambodia signed a treaty that put Cambodia under French protectorate without Siam's acknowledgement. Sri Suriyawongse responded by having King Norodom secretly signed another treaty that recognized Siamese suzerainty over Cambodia. Gabriel Aubaret arrived at Bangkok in April 1864 to be the French consul and started negotiation with Sri Suriyawongse about French-Siamese border proclamations. The Straits Times published the secret Cambodian-Siamese treaty on 20 August 1864,[4] much to the embarrassment of Aubaret who had been unaware of the treaty. Aubaret went directly to King Mongkut to denounce "Kalahom" Sri Suriyawongse. The agreements were delayed and resumed in April 1865 but this treaty was not ratified at Paris as France would recognized Siamese rule over "Siamese Laos". Siam decided to dispatch a mission to Paris in 1865 led by Sri Suriyawongse's son Won Bunnag and the treaty was finally concluded in July 1867,[5] in which Siam recognized French protectorate of Cambodia while in turn France accepted Siamese rule over "Inner Cambodia" (Northwestern Cambodia; Battambang, Siemreap and Sisophon, which had been annexed to Siamese direct rule since 1795 and would be ceded to French Indochina later in 1907.).

Damnoen Saduak Canal was constructed by Chao Phraya Sri Suriyawongse in 1866 - 1868. It hosts the famous Damnoen Saduak Floating Market at Damnoen Saduak District, Ratchaburi Province.

In 1866, King Mongkut commissioned Sri Suriyawongse to oversee the construction of a 35-km long canal that connected Tha Chin River and Mae Klong River to facilitate commuting into Western Siam. The construction was finished in 1868 and was named Damnoen Saduak Canal. As Sri Suriyawongse had spent his own wealth on the construction of the canal, King Mongkut allowed the Bunnags to settle along the canal.[6] In August 1868, Sri Suriyawongse organized the royal outing of King Mongkut to Wa Keo, Prachuap Khiri Khan Province with his son Prince Chulalongkorn to observe the Solar eclipse of August 18, 1868 calculated by the king.

Sri Suriwongse in 1865

After the demise of his father in 1855 and the demise of Vice-King Pinklao in 1866, Sri Suriyawongse emerged as the most powerful courtier. After the solar eclipse event, King Mongkut was exposed to malaria and died in October 1868. Sri Suriyawongse held a council of royal princes and top ministers. The council affirmed that Prince Chulalongkorn, who was fifteen years old, would succeed the throne and Sri Suriyawongse was to be appointed Regent during the minority of the new king. However, Sri Suriyawongse wished Vice-King Pinklao's son Prince Wichaichan be appointed as the Front Palace or heir presumptive. Prince Vorachak objected this, saying that the rights of appointing an heir belonged to the king, but Sri Suriyawongse prevailed. Sri Suriyawongse was succeeded as Samuha Kalahom and as the Commander of Royal Navy by his son Won Bunnag who was made Chao Phraya Surawong Waiyawat in 1869.

In the 1870s, during his Regency, Sri Suriyawongse wielded a great power. King Chulalongkorn later described the situation to Crown Prince Vajiravudh in July 1893; "All of the princes were under Somdet Chao Phraya's power".[7]

At the end of his regency in September 1873 when King Chulalongkorn had reached maturity, Sri Suriyawongse was invested the Somdet Chao Phraya Borom Maha Sri Suriyawongse with honors equal to a prince, the same rank his father had previously received - the highest rank a Siamese noble had ever attained during the Rattanakosin period. Sri Suriyawongse retired to his new estate in Ratchaburi where he spent last nine years of his life.

The retired Sri Suriyawongse became involved in the politics again in an event known as "Front Palace Crisis" in December 1874. Stand-offs between King Chulalongkorn and Prince Wichaichan the Front Palace led to the latter taking refuge in British consulate. Thomas George Knox the British consul-general had been known to support Vice-King Pinklao's lineage and to prevent British intervention King Chulalongkorn requested Sri Suriyawongse for aid. Sri Suriyawongse arrived at Bangkok and managed to convince Prince Wichaichan to leave British consulate.

In January 1883, Sri Suriyawongse fell seriously ill at his estate at Ratchaburi. His eldest son Won Bunnag had him transported in a steamboat from Ratchaburi to Bangkok for treatment but Sri Suriyawongse died en route at Amphoe Krathum Baen, Samut Sakhon Province on 19 January 1883, aged 74. His funeral was held in manners and honors of a royalty.