[1] In 2017 Byambajav participated in the World Championships held in London, placing 46th in the marathon event, with a time of 2:21:48.

On 5 October he represented his country at the 2019 World Championships in Athletics in Doha, Qatar where he finished 40th in 2:20:07.

On 27 October he ran the marathon at the CISM Military World Games in Wuhan, China, where he placed 4th in 2:12:56.

In 2020, Byambajav ran the Beppu-Oita Mainichi Marathon, where he placed 5th in a personal best time of 2:09:03.

This performance qualified him for the 2020 Tokyo Olympic Games men's marathon.