Protesters admonished senators for not supporting Move Forward Party leader Pita Limjaroenrat’s bid to become prime minister.
Political activist Sombat Boonngamanong, also known as “Bor Kor Lai Jud”, claimed that Senate's move had damaged Thailand's democracy, turning the May 14 election into a joke.
Protesters also staged a card stunt in the shape of the consonant “Kho” in the Thai alphabet, asking Senate to think about who has the authority in the country.
Sombat shut down the demonstration at 7.20pm, asking protesters to follow up in the next protest.
Separately, a representative of protesters identifying themselves as "Thatchapong" asked protesters to wear black until the end of July in protest against the Senate.