In 2005, he was appointed as counsellor at the Chinese Embassy in Japan, a position he served till 2007.

On 23 July 2018, during speech at the Royal University of Phnom Penh, Xiong said that the European Union should not exploit Cambodia's political situation to put commercial and economic pressure on it.

[1][4] In April 2020, Báo Thế giới và Việt Nam, the newspaper of the Ministry of Foreign Affairs of Vietnam published an article by Xiong where he highlighted China's bankrolling of projects along the Mekong River.

According to a report by the Center for Naval Analyses, Xiong's article seemed push back against criticism that Chinese projects on Mekong have had a severely negative effect on downriver communities of countries where the river flows through.

[5] On 11 December 2023, ahead of the visit of Chinese President Xi Jinping to Vietnam on 12 December 2023, Xiong announced that China is prepared to provide financial assistance to Vietnam for the enhancement of a railway connection between Guangxi and Hanoi, and that there are additional commitments to accelerate the implementation of initiatives aimed at establishing further railway networks that connect the two nations.