| Singles | |
|---|---|
| 2025 Nonthaburi Challenger II | |
| Champion |  Rio Noguchi |
| Runner-up |  Cui Jie |
| Score | 7–6(11–9), 6–2 |
Aslan Karatsev was the defending champion [1] but lost in the second round to Marat Sharipov.
Rio Noguchi won the title after defeating Cui Jie 7–6(11–9), 6–2 in the final. [2]
Hsu Yu-hsiou (second round)
Francesco Maestrelli (second round)
Gonzalo Oliveira (withdrew) Bai Yan (first round)
Marek Gengel (first round, retired) Sun Fajing (first round)
Geoffrey Blancaneaux (first round)
Rémy Bertola (first round)| Semifinals | Final | ||||||||||||
| Rio Noguchi | 7 | 64 | 6 | ||||||||||
 Murphy Cassone | 5 | 77 | 3 | ||||||||||
| Rio Noguchi | 711 | 6 | |||||||||||
| Cui Jie | 69 | 2 | |||||||||||
 Marat Sharipov | 6 | 3 | 66 | ||||||||||
| Cui Jie | 3 | 6 | 78 | ||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 1 | Y-h Hsu | 6 | 6 | ||||||||||||||||||||||||
| Q | K Isomura | 2 | 1 | 1 | Y-h Hsu | 2 | 1 | ||||||||||||||||||||
| WC |  Maximus Jones | 63 | 6 | 6 | WC | M Jones | 6 | 6 | |||||||||||||||||||
| Q | B Paire | 77 | 3 | 4 | WC | M Jones | 6 | 1 | 0 | ||||||||||||||||||
| WC | Thanapet Chanta | 5 | 3 | R Noguchi | 3 | 6 | 6 | ||||||||||||||||||||
| R Noguchi | 7 | 6 | R Noguchi | 6 | 6 | ||||||||||||||||||||||
| C Denolly | 79 | 4 | 6 | C Denolly | 3 | 3 | |||||||||||||||||||||
| 6 | F Sun | 67 | 6 | 4 | R Noguchi | 7 | 64 | 6 | |||||||||||||||||||
| LL |  N Oberleitner | 4 | 65 | M Cassone | 5 | 77 | 3 | ||||||||||||||||||||
| Q | J Paul | 6 | 77 | Q | J Paul | 6 | 6 | ||||||||||||||||||||
| E Dalla Valle | 6 | 6 | E Dalla Valle | 3 | 4 | ||||||||||||||||||||||
| Q | Hikaru Shiraishi | 0 | 2 | Q | J Paul | 63 | 63 | ||||||||||||||||||||
 O Prihodko | 6 | 3 | 4 | M Cassone | 77 | 77 | |||||||||||||||||||||
| Andre Ilagan | 3 | 6 | 6 | A Ilagan | 2 | 3 | |||||||||||||||||||||
| M Cassone | 6 | 6 | M Cassone | 6 | 6 | ||||||||||||||||||||||
| 8 | R Bertola | 4 | 1 | ||||||||||||||||||||||||
| First round | Second round | Quarterfinals | Semifinals | ||||||||||||||||||||||||
| 5 | M Gengel | 1r | |||||||||||||||||||||||||
| H Moriya | 5 | H Moriya | 4 | 4 | |||||||||||||||||||||||
| Q | Y Takahashi | 2 | 78 | 3 | Q | Y Takahashi | 6 | 6 | |||||||||||||||||||
| M Imamura | 6 | 66 | 1r | Q | Y Takahashi | 3 | 6 | 2 | |||||||||||||||||||
| Marat Sharipov | 6 | 6 | M Sharipov | 6 | 4 | 6 | |||||||||||||||||||||
| Q | Z Kolář | 3 | 4 | M Sharipov | 77 | 5 | 6 | ||||||||||||||||||||
| A Karatsev | 7 | 2 | 77 | A Karatsev | 62 | 7 | 4 | ||||||||||||||||||||
| 4 | Y Bai | 5 | 6 | 62 | M Sharipov | 6 | 3 | 66 | |||||||||||||||||||
| 7 | G Blancaneaux | 0 | 4 | J Cui | 3 | 6 | 78 | ||||||||||||||||||||
| Alt |  D Michalski | 6 | 6 | Alt | D Michalski | 1 | 6 | 77 | |||||||||||||||||||
 J Sels | 77 | 6 | J Sels | 6 | 1 | 61 | |||||||||||||||||||||
| C Tabur | 64 | 3 | Alt | D Michalski | 6 | 3 | 64 | ||||||||||||||||||||
| WC | W Trongcharoenchaikul | 4 | 2 | J Cui | 2 | 6 | 77 | ||||||||||||||||||||
| J Cui | 6 | 6 | J Cui | 6 | 6 | ||||||||||||||||||||||
| Christian Langmo | 6 | 1 | 3 | 2 | F Maestrelli | 4 | 2 | ||||||||||||||||||||
| 2 | F Maestrelli | 4 | 6 | 6 | |||||||||||||||||||||||
Andreas Seppi was the defending champion, but lost in the semifinals to Mikhail Kukushkin.
Richard Gasquet won the title, defeating Kukushkin in the final, 4–6, 6–4, 6–4.
Richard Gasquet was the defending champion, but withdrew before the tournament began.
Marin Čilić won the title, defeating Roberto Bautista Agut in the final, 6–4, 6–4.
Defending champion Marin Čilić defeated Roberto Bautista Agut in the final, 6–4, 6–4 to win the men's singles tennis title at the 2015 Kremlin Cup.
Marin Čilić was the two-time defending champion, but chose not to participate this year.
Kamil Majchrzak was the defending champion but chose not to defend his title.
This was the first edition of the tournament, primarily organised due to the cancellation of many tournaments during the 2020 season, because of the ongoing COVID-19 pandemic.
Jannik Sinner defeated Vasek Pospisil in the final, 6–4, 3–6, 7–6(7–3) to win the singles tennis title at the 2020 Sofia Open. It was his first ATP Tour title.
Matteo Berrettini defeated Aslan Karatsev in the final, 6–1, 3–6, 7–6(7–0) to win the men's singles tennis title at the 2021 Serbia Open.
Aslan Karatsev was the defending champion but chose not to defend his title.
Aslan Karatsev was the defending champion but chose not to defend his title.
John Millman was the defending champion, but lost in the quarterfinals to James Duckworth.
Andrey Rublev was the reigning champion from when the tournament was last held in 2019, but lost to Adrian Mannarino in the second round in a rematch of the 2019 final.
Andrey Rublev was the defending champion, but lost in the quarterfinals to Botic van de Zandschulp.
Aslan Karatsev defeated Andy Murray in the final, 6–3, 6–3 to win the men's singles title at the 2022 Sydney Tennis Classic. This was Murray's first ATP final since he won the 2019 European Open.
Andrey Rublev defeated Jiří Veselý in the final, 6–3, 6–4 to win the men's singles title at the 2022 Dubai Tennis Championships. It was Rublev's tenth career singles title. Veselý entered the tournament ranked as the world No. 123, and was the lowest-ranked finalist in the tournament's history.
Andrey Rublev defeated Novak Djokovic in the final, 6–2, 6–7(4–7), 6–0 to win the singles tennis title at the 2022 Serbia Open.
Matteo Berrettini defeated Andy Murray in the final, 6–4, 5–7, 6–3 to win the singles tennis title at the 2022 Stuttgart Open.
Lorenzo Sonego defeated Alexander Bublik in the final, 7–6(7–3), 6–2 to win the singles tennis title at the 2022 Moselle Open.
Félix Auger-Aliassime defeated Holger Rune in the final, 6–3, 7–5 to win the singles tennis title at the 2022 Swiss Indoors. It was his third title in as many weeks and fourth career ATP Tour singles title overall.
Wu Tung-lin was the defending champion but lost in the first round to Dalibor Svrčina.