# 2018 Seoul Open Challenger – Singles

Thomas Fabbiano was the defending champion but chose not to defend his title.
Mackenzie McDonald won the title after defeating Jordan Thompson 1–6, 6–4, 6–1 in the final.

## Seeds

* Vasek Pospisil (second round)
* Dudi Sela (first round)
* Jordan Thompson (final)
* Lu Yen-hsun (second round, retired)
* Mackenzie McDonald (champion)
* Go Soeda (second round)
* Jason Jung (second round)
* Tatsuma Ito (semifinals)

## 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 | Semifinals | Final | Final | Final | Final | Final |
| | Jason Kubler | 3 | 6 | 4 | | | | | |
| 3 | Jordan Thompson | 6 | 3 | 6 | | | | | |
| 3 | Jordan Thompson | 6 | 3 | 6 | 3 | Jordan Thompson | 6 | 4 | 1 |
| | | | | | 5 | Mackenzie McDonald | 1 | 6 | 6 |
| 5 | Mackenzie McDonald | 6 | 7$^7$ | | 5 | Mackenzie McDonald | 1 | 6 | 6 |
| 8 | Tatsuma Ito | 4 | 6$^4$ | | | | | | |

### Top half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 1 | V Pospisil | 4 | 6 | 6 | | | | | | | | | | | | | |
| | B Schnur | 6 | 1 | 3 | 1 | V Pospisil | 3 | 3 | | | | | | | | | |
| | J Kubler | 6 | 6 | | | J Kubler | 6 | 6 | | | | | | | | | |
| | Ze Zhang | 1 | 1 | | | | | | | J Kubler | 6 | 6 | | | | | |
| | S-w Kwon | 6 | 1 | 6 | | | | | | S-w Kwon | 3 | 4 | | | | | |
| | M Janvier | 1 | 6 | 3 | | S-w Kwon | 6 | 6 | | | | | | | | | |
| | M Giron | 6 | 3 | 4 | 6 | G Soeda | 4 | 4 | | | | | | | | | |
| 6 | G Soeda | 1 | 6 | 6 | | | | | | | | | | J Kubler | 3 | 6 | 4 |
| 3 | J Thompson | 6 | 6 | | | | | | | | | | 3 | J Thompson | 6 | 3 | 6 |
| WC | Kim Young-seok | 1 | 2 | | 3 | J Thompson | 7 | 7$^{11}$ | | | | | | | | | |
| | F Peliwo | 7 | 3 | 1$^r$ | Q | J-h Son | 5 | 6$^9$ | | | | | | | | | |
| Q | Son Ji-hoon | 5 | 6 | 3 | | | | | 3 | J Thompson | 6 | 6 | | | | | |
| Q | Renta Tokuda | 1 | 2 | | | | | | | T-h Yang | 1 | 3 | | | | | |
| | T-h Yang | 6 | 6 | | | T-h Yang | 6 | 7 | | | | | | | | | |
| Q | Makoto Ochi | 4 | 0 | | 7 | J Jung | 4 | 5 | | | | | | | | | |
| 7 | J Jung | 6 | 6 | | | | | | | | | | | | | | |

### Bottom half

| First round | First round | First round | First round | First round | Second round | Second round | Second round | Second round | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Quarterfinals | Semifinals | Semifinals | Semifinals | Semifinals |
| 5 | M McDonald | 7 | 6 | | | | | | | | | | | | | | |
| WC | U-s Park | 5 | 2 | | 5 | M McDonald | 6 | 6 | | | | | | | | | |
| SE | K Majchrzak | 6 | 6 | | SE | K Majchrzak | 3 | 4 | | | | | | | | | |
| | Y Takahashi | 2 | 3 | | | | | | 5 | M McDonald | 6$^4$ | 7$^{10}$ | 6 | | | | |
| | L Harris | 5 | 6 | 6 | | | | | | L Harris | 7$^7$ | 6$^8$ | 3 | | | | |
| WC | Y-s Chung | 7 | 3 | 0 | | L Harris | 6 | 3 | | | | | | | | | |
| | M Banes | 4 | 1 | | 4 | Y-h Lu | 4 | 0$^r$ | | | | | | | | | |
| 4 | Y-h Lu | 6 | 6 | | | | | | | | | | | 5 | M McDonald | 6 | 7$^7$ |
| 8 | T Ito | 6 | 6 | | | | | | | | | | | 8 | T Ito | 4 | 6$^4$ |
| | D-h Lee | 1 | 3 | | 8 | T Ito | 7 | 6 | | | | | | | | | |
| | Y Uchiyama | 6 | 4 | 5 | WC | S-c Hong | 5 | 1 | | | | | | | | | |
| WC | S-c Hong | 2 | 6 | 7 | | | | | 8 | T Ito | 7 | 3 | 6 | | | | |
| Q | Yo Watanuki | 6 | 6 | | | | | | | D Wu | 5 | 6 | 2 | | | | |
| | D Kelly | 3 | 4 | | Q | Yo Watanuki | 4 | 5 | | | | | | | | | |
| | D Wu | 6 | 2 | 6 | | D Wu | 6 | 7 | | | | | | | | | |
| 2 | D Sela | 3 | 6 | 0 | | | | | | | | | | | | | |