| 2026 Nonthaburi Challenger II | |
|---|---|
| Date | 12 – 17 January |
| Edition | 15th |
| Surface | Hard |
| Location | Nonthaburi, Thailand |
| Champions | |
| Singles | |
 Pol Martín Tiffon | |
| Doubles | |
 Sriram Balaji /  Neil Oberleitner | |
The 2026 Nonthaburi Challenger II was a professional tennis tournament played on hard courts. It was the 15th edition of the tournament which was part of the 2026 ATP Challenger Tour. It took place in Nonthaburi, Thailand from 12 to 17 January 2026.
| Country | Player | Rank1 | Seed |
|---|---|---|---|
 JPN | Rio Noguchi | 227 | 1 |
 KAZ | Timofey Skatov | 235 | 2 |
 CHN | Zhou Yi | 248 | 3 |
 POL | Daniel Michalski | 249 | 4 |
| JPN | Kaichi Uchida | 251 | 5 |
| AUT | Joel Schwärzler | 254 | 6 |
 USA | Andres Martin | 269 | 7 |
| CHN | Sun Fajing | 274 | 8 |
The following players received wildcards into the singles main draw:
The following player received entry into the singles main draw using a protected ranking:
The following players received entry from the qualifying draw:
Chung Hyeon 
Marek Gengel 
Philip Henning Christian Langmo Neil Oberleitner Yasutaka Uchiyama The following player received entry as a lucky loser:
Andre Ilagan Pol Martín Tiffon def. 
Maximus Jones 6–4, 3–6, 6–4. Sriram Balaji / Neil Oberleitner def. Anirudh Chandrasekar / Takeru Yuzuki 6–3, 7–6(8–6).