Under the 2017 constitution drafted under the National Council for Peace and Order (NCPO—the military junta in power from 2014 to 2019), the 500 members of the House of Representatives are elected using a form of mixed-member proportional representation, in which voters cast a single vote. 350 seats are elected from single-member constituencies by first-past-the-post voting, with the remaining 150 being levelling seats, allocated to ensure parties receive a number of seats proportionate to their national vote total.[3] As in the preceding 2019 election, the parliament's vote for Prime Minister will take place in a joint session with the 250-seat senate, according to the constitution's provisional terms. As the term of the NCPO-appointed senate lasts until 2024, it is expected to exert influence into this election as well.[4]
2021 restoration of parallel voting system[]
On 10 September 2021, a joint session of both houses of parliament voted by a margin of 472 to 33 (with 187 abstentions) to restore the pre-2017 parallel voting system, with 400 seats elected from single-member constituencies by first-past-the-post voting, an increase of 50, and reduced the number of party-list lawmakers to 100 from 150 (retaining a total of 500 seats for the lower house). Unlike the current system which meant only one vote was cast by each voter to determine both constituency and leveling seats, the earlier system of casting two ballots - one for a constituency candidate in 400 seats and another for a political party list was restored for the 100 seats. The reform is subject to approval by King Vajiralongkorn.[5] However, the change was criticised by smaller parties as the system makes it harder for such parties to win seats, and the change is likely to benefit the ruling Palang Pracharath Party and the opposition Pheu Thai Party.
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