Singler attended South Medford High School where he was the 2009 OSAA 6A State Player of the Year after averaging 21.8 points, 10.8 rebounds, 5.0 assists, 1.4 blocks and 1.0 steals per game as a senior, helping the Panthers to a 21-8 record and a sixth-place finish at the OSAA Class 6A tournament. He also was named the 2009 Gatorade Oregon Boys Basketball Player of the Year and the Southwest Conference Player of the Year.
In his senior year with the Oregon Ducks, Singler averaged 11.7 points, 4.9 rebounds, and 2.8 assists in 31 minutes per game as the Ducks advanced to the Sweet 16 of the NCAA Tournament.
After going undrafted in the 2013 NBA draft, Singler joined the Detroit Pistons for the 2013 NBA Summer League. On September 4, 2013, he signed with the Portland Trail Blazers. However, he was later waived by the Trail Blazers on October 22 after appearing in two preseason games. In November 2013, he was acquired by the Idaho Stampede of the NBA Development League.
On September 8, 2014, Singler signed with Estonian club BC Kalev/Cramo for the 2014–15 season. He appeared in 60 games for the club, averaging 6.9 points and 3.4 rebounds per game.
On October 21, 2015, Singler signed with the Utah Jazz, but was waived the next day. On November 1, he returned to the Idaho Stampede. On November 13, he made his season debut for Idaho in a 110–106 loss to the Rio Grande Valley Vipers, recording 20 points, five rebounds, two assists and three steals in 36 minutes. On March 4, 2016, he was traded to Raptors 905 in exchange for a 2016 second-round draft pick. On March 11, he made his debut for Raptors 905 in a 102–98 win over the Iowa Energy, recording 12 points, two rebounds and three assists in 27 minutes off the bench.
In July 2016, Singler joined the Toronto Raptors for the 2016 NBA Summer League. On September 8, 2016, he signed with Toronto, but was waived on October 22 after appearing in four preseason games. On October 30, 2016, he was reacquired by Raptors 905.
Singler's father, Ed, played quarterback at Oregon State between 1978 and 1982, while his mother, Kris, played basketball also at Oregon State between 1973 and 1976. His older brother, Kyle, is also a professional basketball player.