Parkes was appointed as the British consul in Amoy in 1854. In 1855, he accompanied Bowring to Siam as a joint secretary of the diplomatic mission to conclude a commercial treaty between the British and Siamese. The treaty, known as the Bowring Treaty, was signed in Bangkok on 18 April. Parkes then returned to Britain with the Bowring Treaty for it to be ratified by the British government. He delivered it on 1 July and was received by Queen Victoria on 9 July. He spent the rest of the year helping the Foreign Office with Chinese and Siamese business. He exchanged the ratified Bowring Treaty in Bangkok on 5 April 1856 and arrived in Canton in June to serve as the acting British consul during Alcock's absence.