Big Brother Thailand 1 was the first season of the Thailand reality television series Big Brother Thailand and aired on iTV's primetime block. The season started on 6 April 2005 and ended on 16 July 2005, lasting 106 days. It was the most talk-about season of Big Brother Thailand.
Twelve housemates entered the house together on the first night. Each week, except for the first week, one of them would be evicted by the public vote. Due to Yinmy's ejection from the house on Week 11, Pim returned to the house to replace her. On the final night, the public voted for the housemate(s) they wanted to win, and Nipon Perktim (Tui) was the winner.