It earlier voted 122:19 to appoint Supa Piyajitti, a former deputy finance permanent secretary, as a national anti-corruption commissioner, replacing a retiring member.
Ms Supa is widely known as the whistleblower when she said the rice-pledging scheme is susceptible to corruption at every stage.
Four senators were vying for the speaker's seat.
All eyes were on the speaker vote because anti-government forces, including the Democrat Party, are pushing for him to appoint a new interim prime minister and/or interim cabinet.
The strongest candidate was Surachai Liangboonlertchai, an appointed senator, incumbent first deputy speaker and acting speaker.
He was backed by the "40 Senators" group (an alliance of 40 appointed senators), the People's Democratic Reform Committee (PDRC), and the elected senators from the South mainly affiliated with the Democrat Party.
Pol Gen Jongrak Jutanont, an appointed senator, is widely perceived as being supported by the Pheu Thai Party although he has never made clear his affiliation. He was believed to have 10 friends in the appointed faction.
Srimuang Charoensiri, the elected senator for Maha Sarakham, is believed to have a direct link with the Shinawatra family.
Jongchai Thiangtham, the elected senator for Suphan Buri, is linked to the Chart Thai Pattana Party.
The Senate now consists of 77 newly elected senators and 73 appointed members.
People's Democratic Reform Committee (PDRC) secretary general Suthep Thaugsuban brought his supporters to parliament to submit a letter to Mr Surachai, as acting senate speaker, asking him to help solve the crisis. The contents of the letter were not announced.