# 2025 Nonthaburi Challenger III – Singles

Rio Noguchi was the defending champion but lost in the second round to Murphy Cassone.
Brandon Holt won the title after defeating Vít Kopřiva 6–3, 6–2 in the final.

## Seeds

* Vít Kopřiva (final)
* Hugo Grenier (quarterfinals)
* Valentin Vacherot (first round)
* Zachary Svajda (quarterfinals)
* Shintaro Mochizuki (second round)
* Coleman Wong (second round)
* Henri Squire (second round)
* Dmitry Popko (first round)

## Draw
### Key

* Q = Qualifier
* WC = Wild card
* LL = Lucky loser
* Alt = Alternate
* SE = Special exempt
* PR = Protected ranking
* ITF = ITF entry
* JE = Junior exempt
* w/o = Walkover
* r = Retired
* d = Defaulted
* SR = Special ranking

### Finals

| Semifinals | Semifinals | Semifinals | Semifinals | Final | Final | Final | Final |
| 1 | Vít Kopřiva | 6 | 6 | | | | |
| Q | Murphy Cassone | 2 | 2 | | | | |
| Q | Murphy Cassone | 2 | 2 | 1 | Vít Kopřiva | 3 | 2 |
| | | | | | Brandon Holt | 6 | 6 |
| | Brandon Holt | 6 | 6 | | Brandon Holt | 6 | 6 |
| Q | Clément Tabur | 2 | 4 | | | | |

### Top half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | V Kopřiva | 6 | 6 | | | | | | | | | | | | | | |
| | N Hardt | 4 | 1 | | 1 | V Kopřiva | 6 | 7$^7$ | | | | | | | | | |
| | FC Jianu | 2 | 2 | | Alt | T-l Wu | 4 | 6$^4$ | | | | | | | | | |
| Alt | T-l Wu | 6 | 6 | | | | | | | 1 | V Kopřiva | 6 | 6 | | | | |
| | E Couacaud | 3 | 2 | | | | | | | | D Svrčina | 0 | 1 | | | | |
| | D Svrčina | 6 | 6 | | | D Svrčina | 6 | 6$^4$ | 6 | | | | | | | | |
| WC | Maximus Jones | 6$^0$ | 0$^r$ | | 7 | H Squire | 4 | 7$^7$ | 1 | | | | | | | | |
| 7 | H Squire | 7$^7$ | 0 | | | | | | | | | | | 1 | V Kopřiva | 6 | 6 |
| 3 | V Vacherot | 1 | 6 | 6$^2$ | | | | | | | | | | Q | M Cassone | 2 | 2 |
| Q | M Cassone | 6 | 4 | 7$^7$ | Q | M Cassone | 6 | 6 | | | | | | | | | |
| | T Skatov | 1 | 3 | | Q | R Noguchi | 3 | 4 | | | | | | | | | |
| Q | R Noguchi | 6 | 6 | | | | | | | Q | M Cassone | 6 | 6 | | | | |
| | S Shimabukuro | 2 | 6 | 6 | | | | | | Alt | F Arnaboldi | 4 | 1 | | | | |
| | A Escoffier | 6 | 2 | 1 | | S Shimabukuro | 6 | 6$^4$ | 4 | | | | | | | | |
| Alt | F Arnaboldi | 6 | 2 | 6 | Alt | F Arnaboldi | 1 | 7$^7$ | 6 | | | | | | | | |
| 8 | D Popko | 1 | 6 | 1 | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 6 | C Wong | 7$^7$ | 7$^7$ | | | | | | | | | | | | | | | |
| | B Hassan | 6$^2$ | 6$^4$ | | 6 | C Wong | 4 | 1 | | | | | | | | | | |
| | B Holt | 6 | 6 | | | B Holt | 6 | 6 | | | | | | | | | | |
| WC | W Trongcharoenchaikul | 3 | 3 | | | | | | | | B Holt | 6$^7$ | 6 | 6 | | | | |
| | K Sultanov | 4 | 6 | 3 | | | | | | 4 | Z Svajda | 7$^9$ | 3 | 4 | | | | |
| | Y Shimizu | 6 | 3 | 6 | | Y Shimizu | 6 | 3 | 2 | | | | | | | | | |
| Q | F Sun | 3 | 2 | | 4 | Z Svajda | 4 | 6 | 6 | | | | | | | | | |
| 4 | Z Svajda | 6 | 6 | | | | | | | | | | | | | B Holt | 6 | 6 |
| 5/Alt | S Mochizuki | 7$^7$ | 7 | | | | | | | | | | | | Q | C Tabur | 2 | 4 |
| Q | R Bertola | 6$^0$ | 5 | | 5/Alt | S Mochizuki | 2 | 4 | | | | | | | | | | |
| Q | C Tabur | 6 | 6 | | Q | C Tabur | 6 | 6 | | | | | | | | | | |
| Q | F Maestrelli | 2 | 1 | | | | | | | Q | C Tabur | 7 | 6 | | | | | |
| | L Neumayer | 6 | 4 | 2 | | | | | | 2 | H Grenier | 5 | 4 | | | | | |
| | E Spizzirri | 3 | 6 | 6 | | E Spizzirri | 4 | 4 | | | | | | | | | | |
| WC | Thanapet Chanta | 2 | 0 | | 2 | H Grenier | 6 | 6 | | | | | | | | | | |
| 2 | H Grenier | 6 | 6 | | | | | | | | | | | | | | | |