Fixing the organic law on elections in line with the latest charter amendment could run afoul of the constitution, making it likely the Constitutional Court will be asked to rule on the issue, say legal experts.
The charter amendment to revert from the single-ballot election to the two-ballot method was approved by parliament last week.
The next step is to forward the bill for royal endorsement within 15 days of it being approved by parliament.
Paiboon Nititawan, deputy leader of the ruling Palang Pracharath Party and former chairman of the amendment committee, said on Saturday a restored dual-ballot method would necessitate rewriting the organic law on elections as well.
In the organic law, the clauses on electing constituency MPs and calculation of list MPs must be replaced with a system to accommodate the two-ballot method.
Mr Paiboon said that after the bill takes effect, the organic law will be reworked. He will propose the law be rewritten using the 1997 constitution, under which the two-ballot method was applied, as a prototype.
Mr Paiboon said he will also propose in the rewriting of the organic law that only parties which fielded more than 100 constituency candidates be eligible to receive list MPs.
"The number of MPs fielded speaks to a party's commitment to politics," he said.
The proposed rewriting of the organic law, however, risks contravening the constitution. This is because sections of the charter related to the calculation of list MPs are still based on the current single-ballot, mixed-member proportional (MMP) election system.
Somchai Srisuthiyakorn, a former election commissioner, said some key words related to the MMP system have not been removed from Sections 93 and 94 of the charter.
The MMP system is enshrined in the principle that every vote, even those cast for a defeated candidate, counts toward a party's vote tally.
If the organic law is redrafted to specify anything that goes against such principle, it will be deemed as contradicting the charter, he said.
Jade Donavanik, a former adviser to the 2017 Constitution Drafting Committee, said if Mr Paiboon insists on calculating list MPs to conform to the dual-ballot method without first fixing the two sections, the issue could end up in the Constitutional Court.