Teh won the bronze medal as he was in the men's team at the
2019 SEA Games, where Singapore finished as semi-finalists. In 2021, he achieved two runner-up positions at the
Polish International and the
Bahrain International. He was also a semifinalist at the
Czech Open. In February 2022, he and his team were semifinalists at the
Badminton Asia Team Championships. In early May 2022, Jason played as the 2nd men singles for the Singaporean Squad at the Thomas Cup. In the first group match against Indonesia, Teh lost to
Jonatan Christie in straight games, 19–21, 13–21. Singapore eventually lost 1–4 overall. The next day, during Singapore's group match against South Korea, Teh was playing against
Jeon Hyeok-jin. When Teh was 14–7 up in the first set, he slipped and injured his right foot, which required immediate treatment. Teh got up and started to play again, winning the first set 21–14. During the 2nd set, at 1–3 down, Teh twisted his right foot, adding a 2nd injury to his right leg. Teh eventually lost the 2nd and 3rd sets, thus losing the match 21–14, 13–21, 14–21. Singapore narrowly lost 2–3 overall in the group match, which meant that Singapore did not advance to the group stage. Two days later, in the final group match against Thailand, Jason played against
Adulrach Namkul. He lost in rubber games, 21–23, 21–14, 17–21. Singapore ended its 3rd Thomas Cup campaign by losing 2–3 to Thailand. A week later, Teh was in the men's team and the men's singles event at the
2021 SEA Games, entering the semifinals of the men's team In the Individual event, he got into the semifinals by beating
Chico Aura Dwi Wardoyo of Indonesia. He then lost to Thailand's
Kunlavut Vitidsarn in the semifinals, in straight games, 11–21, 12–21, thus ending up with the joint bronze medal. At the
2022 Commonwealth Games, Teh won the bronze medal in the mixed team event as the Singaporean team finished as bronze medalists at the event after defeating England 3–0. A few days after the Mixed team event, Teh took part in the
men's singles as the 7th seed. Teh lost to
Srikanth Kidambi in the bronze medal match, losing 15–21, 18–21 in straight games. Teh finished 4th place overall. Teh won the bronze medal as he was in the men's team at the
2023 SEA Games, where Singapore finished in the semi-finals.
2024–2025 In 2024, Teh was the runner-up in two
BWF International Challenge competitions: the
Polish Open in March and the
Luxembourg Open in May. He also performed well in the
BWF World Tour tournaments by reaching the semi-finals of the
U.S. Open in June and the
Vietnam Open in September. During the last week of September, Teh reached his first BWF World Tour final at the
Macau Open, finishing second to Hong Kong's
Ng Ka Long. He continued his fine run in the BWF World Tour and reached another final at the
Malaysia Super 100 in October. However, his search for the first international badminton title was dashed by Taiwanese
Chi Yu-jen after losing in the rubber set 12–21, 23–21, 15–21. In November, Teh took part in the
Syed Modi India International, another BWF World Tour 300 event. Seeded fourth, Teh upset home favourite second seed
Priyanshu Rajawat through his superb net play and won 21–13, 21–19 to advance to his second men's singles final in two months. However, Teh could not replicate his fine form in the final and was outclassed by India's top seed,
Lakshya Sen. He was trumped 6–21, 7–21 in just 31 minutes. Teh claimed his first BWF World Tour title in the
Thailand Masters after beating Wang Zhengxing in the final. After the first success, Teh suffered multiple early exits in his next 16 tournaments. His second title came 10 months later in the South Korean city of Iksan when he defeated Japanese Yudai Okimoto 21-14, 21-15 in the men's singles final of the
Korea Masters.
2026 Teh returned to the podium in March 2026 by winning the
Polish Open title, a BWF International Challenge event, beating
Koshiro Moriguchi from Japan in straight games, 21–9, 21–10, in the final. == Personal life ==