She is known for her collaboration song with SoulJa, "Koko ni Iru yo", and her answer song "Soba ni Iru ne". In September 2008, the Guinness World Records certified that "Soba ni Iru ne" was the best-selling digital download single in Japan with over two million "full-track" downloads (Chaku Uta Full). Including various forms of digital downloads, it sold over 8.7 million downloads by November 2008. The Guinness record was surpassed by Greeeen's song "Kiseki" in June 2009.
She spent six years at Osaka International School as an elementary school student. At age 12, her family moved to Torrance, California, where she lived for two years and attended Calle Mayor Middle School. She returned to Japan in the winter of 2002, settling in Tokyo. Aoyama attended the American School in Japan. She attended Sophia University.
Aoyama was inspired to become a performer by Janet Jackson. Her first release in the music world was a collaboration on DS455's single "Summer Paradise: Risin' To Tha Sun, feat. Aoyama Thelma". The single reached #46 on the Oricon charts. On September 9, 2007, Aoyama made her solo debut with the single "One Way". This single debuted at #98 on the Oricon charts. Two weeks later, Aoyama was featured on the hit single "Koko ni Iru yo" with fellow J-Soul artist SoulJa. The single stayed on the charts for many weeks. The single sold over 100,000 copies and reached #6 on the charts.
In early 2008, Aoyama released an answer song to the single "Koko ni Iru yo" by SoulJa with her own single titled "Soba ni Iru ne" which also featured SoulJa. The songs are similar, and share the same chorus. However, the song "Soba ni Iru ne" proved to be more popular than the song "Koko ni Iru yo", debuting at #3 in its first week on the Oricon charts, and in its second week reached #1 on the charts. "Soba ni Iru ne" stayed in the Top 5 ranking for 7 consecutive weeks. It became the highest-selling female single (strictly a duet song) on the Oricon 2008 yearly charts.
Her debut album, Diary, was released in Japan on March 26, 2008.
On February 11, 2009, she released the album Love!: Thelma Love Song Collection, which debuted at the number-one position on the Oricon weekly charts. Her album Emotions was released in September, 2009.
Aoyama collaborated with Big Bang's Taeyang for her single, "Fall in Love", released on January 27, 2010.
Aoyama's single "Kaeru Basho" was released on March 3, 2010. The song was used in the movie Doraemon: Nobita's Great Battle of the Mermaid King. This single features SoulJa, and has a B side called "Anata ga Kiechaisode". Summer Love!! featuring Red Rice came out in 2010.
In 2010, she sang with the Taiwan pop group Da Mouth in a duet with the female lead singer Aisa, on the song "Secret Life". The song appears on the album Da First Episode.
Aoyama collaborated with Korean girl group 4Minute on the single, "Without U", released on May 25, 2011. The English version was released on May 7, 2011.
She contributed a cover of hide's "Tell Me" to the Tribute VI -Female Spirits- tribute album, which was released on December 18, 2013.Diary (2008)
Lonely Angel (2014)