He currently plays for Sandvikens IF, wearing the number 9 shirt. He plays primarily as a Forward. His current market value is estimated at 100K €.

His most recent move was a Free from Lunds BK to Sandvikens IF on 2025-01-29.

In the Sweden Superettan 2025 season, william thellsson scored 2 goals and provided 1 assists across 21 appearances, averaging 0.1 goals per game with 0 shots attempted and 0 on target.