A joint sitting of parliament on Wednesday rejected a charter amendment bill which would have ended senators' role in the election of the prime minister.
The bill was presented by Somchai Srisutthiyakorn of the opposition Seri Ruam Thai Party.
It needed a majority of active MPs, at least 364, and at least one-third of senators, or 84.
The bill received votes in favour from 333 MPs and 23 senators, while 102 MPs and 151 senators voted against it. Eight MPs and 45 senators abstained.
It was the last of four bills that were voted on. The other three bills governed the rights of individuals and communities, the rights and liberty of people, and the qualifications of a prime minister and how he or she comes to power.
The bill on the elimination of the senators' right to co-elect a prime minister was sponsored by 64,151 people who signed up to have the legislation presented to parliament. Mr Somchai spearheaded the mass signature campaign.
At around 9pm on Wednesday, a total of 727 parliamentarians voted on the four bills, all of which were rejected. The fourth bill on ridding the senators of their prime minister-selection power received the least support, with 333 votes.
The four bills were backed by parties represented in parliament although the majority of senators voted not to adopt them.
The minority senators included Kanachanrat Leeviroj, Khamnoon Sitthisamarn, Panthep Klanarongran, Dr Porntip Rojanasunan, Naowarat Pongpaiboon, Wanchai Sornsiri, Gen Lertrat Rattanawanich and Wanlop Tangkananurak.
Pita Limjaroenrat, leader of the opposition Move Forward Party (MFP), said senators' involvement in the election of the prime minister was not democratic and his party would campaign for a referendum asking people if the country should have a new constitution.
He also asked senators to vote for a prime ministerial candidate who reflected the outcome of the general election.
Mr Pita said he was especially disappointed with Wednesday night's results to drop the bills that would have vastly improved the current constitution that is riddled with flaws.
The least senators could do is give a wide berth to the process of electing a prime minister after the next general election, he added.
The MFP is launching the so-called "Reset Thailand, New Elections, New Constitution", urging at least 50,000 people to sign in support of a petition to be submitted to the cabinet calling for a referendum to rewrite the entire charter.
The campaign will call for a constitutional drafting assembly to be formed, whose members will be elected by the people. Mr Pita said the sign-up campaign will start soon and he proposed that the referendum be held the same day as the next election expected in May next year.