Chantra came through the Shell Advance Asia Talent Cup, winning the championship in 2016. He then competed in the FIM CEV Moto3 Junior World Championship across 2017 and 2018, showing improving pace but unable to break onto the podium. In 2018 he was given a Moto3 wild-card at his home Thailand Grand Prix and seized the opportunity by finishing ninth, scoring seven points and earning himself a full-time Moto2 contract for the following year.
Chantra spent six full seasons in Moto2 with the Idemitsu Honda Team Asia, a squad created specifically to provide Asian riders with a pathway through the intermediate class.
His debut 2019 campaign yielded 23 points, making him the clear standout among the Honda Asia Team's roster in his first year. The 2020 season was difficult, with points scored in only two races and a final tally of ten points.
From 2021 onwards Chantra became steadily more competitive. His 2021 season brought 37 points, his best finish a fifth place in Austria. He registered his first Moto2 race win during the 2022–2024 period and ultimately claimed two victories in the intermediate class before graduating to MotoGP.
On 29 August 2024 it was confirmed that Chantra would replace the retiring Takaaki Nakagami at LCR Honda for the 2025 MotoGP season, becoming the first Thai rider to sign a MotoGP contract. His teammate was the experienced Johann Zarco.
Chantra had a difficult debut premier-class campaign. After the Spanish Grand Prix he underwent arm pump surgery that forced him to miss several rounds. While recovering, a collateral ligament injury to his right knee sustained during off-road training in July 2025 caused him to sit out the German, Czech, and Austrian Grands Prix. He scored his first MotoGP point at the Dutch TT in Assen.
In September 2025 it was announced that Chantra would not continue with LCR Honda beyond the end of the season, with Diogo Moreira confirmed as his replacement.
Chantra's move to the Superbike World Championship was announced on 30 September 2025, when Honda confirmed he would join the HRC factory WorldSBK team for 2026 alongside Jake Dixon. The switch followed a familiar pattern of Honda using its WorldSBK structure to retain and develop riders after their MotoGP stints.
Chantra's arrival in MotoGP was a milestone for Southeast Asian motorsport. The Asia Talent Cup programme, which he won in 2016, was designed to create exactly this kind of pipeline, and Chantra was only the second of its graduates — after Ai Ogura — to reach MotoGP, both starting in the 2025 season. His presence opened a door for Thai motorcycle racing that no rider had managed before at Grand Prix level's premier class.