The Senate will meet on Tuesday to vote on the referendum bill on constitutional amendments with majority of senators expected to stand firmly by the divisive double-majority rule.
The vote will be held after a joint MP-Senate committee voted to endorse the double-majority rule required for winning a charter rewrite referendum.
Pisit Apiwatthanapong, spokesman of the committee on Senate affairs, confirmed the vote will be taken on Tuesday in the Senate.
The procedure dictates that after the joint committee resolves to second the double-majority requirement, each chamber will separately hold a vote on the rule.
In this case, the Senate's vote is on Tuesday and the House of Representatives will hold theirs on Wednesday.
Prior to the formation of the joint meeting, the MPs and senators had been heavily at odds over the requirement; the House advocated a single majority requirement in approving a referendum while the majority senators insisted on the double majority rule.
Under the old rule, more than 50% of voters must participate in the referendum, and the majority of those who cast their votes must approve it.
With the single majority, a winning vote of any size is deemed valid.
The conflict between the two Houses prompted the joint panel to be established to iron out the differences. However, Senate members of the panel had their way and beat MP members in their vote to retain the disputed clause.
It is therefore likely the senators will rally behind the double majority again and overrule the House and push back the bill's passage.
This will usher in a 180-day "cooling-off period", raising concern it may not be ratified then within the life of the current government.
Sen Pisit on Sunday said the senators will be given a free hand to debate the referendum.
"Opinions may differ but they don't necessarily amount to full-blown conflict.
"Whether one is in the majority, or the minority isn't the point. What matters is we, as senators, must exercise our duty and express our thoughts," he said.
