He played his entire career in the Philippine Basketball Association (PBA) with the Alaska Aces, where his jersey number is retired.

Joachim Thoss was born on December 7, 1981, in Papua New Guinea[1] to a German father and to a Filipina mother.

Basketball competitions in Papua New Guinea are rare; Thoss only represented his high school in one-day tournaments.

[2] In his early years, Sonny was the backup center for the Aces behind the dominant big men Ali Peek and E.J.

But in his later years, Thoss eventually became Alaska's starting big man and become one of the team's top players.

[4] The Aces were able to bounce back in that year's Fiesta Conference finals, by defeating the San Miguel Beermen in five games.

[8] 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.

[12] 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.

[12] He raised his game further in the finals, averaging 14 points and close to 10 rebounds, while playing a huge defensive role in neutralizing Barangay Ginebra import Vernon Macklin.

[20] In the 2014–15 Philippine Cup finals, Thoss matched up with June Mar Fajardo, where the Beermen beat the Aces in seven games.

[30] At first, he wasn't allowed to play in the FIBA Asia Cup that year, as Alaska team owner Wilfred Uytengsu insisted that he practice with the Aces instead after a dismal record the previous season.

[33] In 2015, Thoss was the backup big man for naturalized player Andray Blatche during the 2015 FIBA Asia Championship.