He was the 5th overall pick in the
2004 PBA draft selected by the
Alaska Aces and he was also the tallest rookie picked in that class. In the
2009–10 Philippine Cup finals, Thoss and the Aces were swept by the
Purefoods TJ Giants. The Aces were able to bounce back in that year's
Fiesta Conference finals, by defeating the San Miguel Beermen in five games. In 2011, he was awarded the
PBA Sportsmanship Award. In 2012, he and Alaska finished with a 10-22 record. In the
2012–13 Philippine Cup, the Aces started the season with two straight losses. But the Aces were able to get their first win of the season despite Thoss suffering from a bum stomach against the
Barako Bull Energy Cola. Despite having zero points, he had six rebounds and four blocks. In the
2013 Commissioner's Cup, he earned Player of the Week honors for the week of March 4–10. He then missed several games during the Commissioner’s Cup due to a bad back. But once the playoffs began, the 31-year-old veteran center helped the top-seeded Aces to victories over the
Air21 Express in the quarterfinals, before dethroning the
San Mig Coffee Mixers following a 3–1 series win in the semifinals. He was also on the Mythical Second Team and
All-Defensive Team that season. In the
2013–14 Philippine Cup, Thoss grabbed 11 rebounds in a win over San Mig Coffee. Some games later, he had a career-high 30 points in an overtime loss to the
Talk N' Text Tropang Texters. The Aces failed to defend their Commissioner's Cup title that year. He was named to the Mythical Second Team and the All-Star team for that season. After the season, he, together with
JVee Casio and
Cyrus Baguio, re-signed with the Aces. In the
2014–15 Philippine Cup finals, Thoss matched up with
June Mar Fajardo, where the Beermen beat the Aces in seven games. They matched up again in the
2015–16 Philippine Cup finals, from Game 5 up to the end of the series. San Miguel won that series despite Alaska holding a 3–0 series lead at first. He struggled in that series. He also had five rebounds and two assists in that game, giving him Player of the Week honors. In 2018, he also participated in the Obstacle Challenge during
All-Star Week. The Aces also made the
finals for the Governors' Cup, where they lost to the
Magnolia Hotshots in six games. In 2019, he scored 21 points against the
NLEX Road Warriors to send the Aces to the
Philippine Cup playoffs. On May 17, 2021, Coach
Jeffrey Cariaso announced that Thoss had retired. == National team career ==