Electoral system for national legislature

Thailand, Constitution 2017, accessed 21 February 2019

SECTION 83. The House of Representatives consists of five hundred members, as follows:

1. three hundred and fifty members elected on a constituency basis;

2. one hundred and fifty members from party lists of political parties.

SECTION 85. Members of the House of Representatives who are elected on a constituency basis shall be elected by direct suffrage and secret ballot. Each constituency shall elect one member, and each person having a right to vote has the right to cast one vote in an election, where a vote may be cast in favour of any candidate for election, or no candidate at all.

The candidate for election who receives the highest number of votes and has more votes than votes to elect no candidate shall be the elected member.

The rules, procedures and conditions for the application to stand for election, the casting of votes, the counting of votes, the calculation of total votes, the announcement of the results of the election and other related matters shall be in accordance with the Organic Act on Election of Members of the House of Representatives. Such law may also require a candidate for election to submit evidence of payment of income tax for the application to stand for election. […]

SECTION 91. The calculation of the number of Members of the House of Representatives on a party list basis for each political party shall be made in accordance with the following rules:

1. the total number of votes received throughout the country by all political parties sending candidates for election on party list basis from the election on a constituency basis shall be divided by the number of five hundred, which is the total number of Members of the House of Representatives;

2. the result under (1) shall be used to divide the number of votes received throughout the country by each political party from all constituencies in the election on a constituency basis; the quotient shall be deemed the number of Members of the House of Representatives distributed to that political party;

3. the number of Members of the House of Representatives distributed to the political party under (2) shall be subtracted by the total number of members of House of Representatives attained by such political party on a constituency basis in all constituencies, the result of which shall be the number of Members of the House of Representatives on a party list basis allocated to the political party;

4. if any political party has Members of the House of Representatives who have been elected on a constituency basis equal to or more than the number of Members of the House of Representatives distributed to that political party under (2), that political party shall have Members of the House of Representatives in accordance with the number of Members of the House of Representatives which have been elected on a constituency basis, and shall not be entitled to allocation of Members of the House of Representatives on a party list basis; the total number of Members of the House of Representatives on a party list basis shall be allocated proportionally among political parties having a number of Members of the House of Representatives on a constituency basis that is lower than the number of Members of the House of Representatives distributed to that political party under (2), provided that this shall not result in any political party having more Members of the House of Representatives than the number distributed to that political party under (2);

5. when the number of Members of the House of Representatives on a party list basis of each political party is determined, the candidates for election named in the list of candidates in the numerical order specified in the list of candidates of that political party shall be elected as Members of the House of Representatives.

In the case where any candidate for election dies after the date on which the application for election is closed, but prior to the time the poll is closed on the election date, the number of votes received shall also be used in the calculation under (1) and (2).

The counting of votes, the rules and procedures for calculation, the calculation of proportion and the announcement of the results of the election shall be in accordance with the Organic Act on Election of Members of the House of Representatives.

Thailand, Organic Act on Election of Members of the House of Representatives B. E. 2561 (2018), [text of the law is not available online]

Section 128. In the case where there is announcement of election result for all constituencies, calculation to accommodate members of the House of Representatives under party list basis of each political party having nominated candidates under party list basis ought to receive, calculation shall be done under following rules, with four digits of decimal notation being applied for fraction:

(1) collect all votes received from each constituency countrywide of every party nominating candidates under party list basis, divided by five hundred which is the total number of members of the House of Representatives;

(2) take the result under (1) divided by number of votes throughout the country each party received from all polling stations under constituency basis, the numeral figures shall be the initial number of seats of the House of Representatives of that political party, and when the calculation being done following (5), (6) or (7) if it’s in case, then it shall be deemed as number of members of the House of Representatives that political party ought to have;

(3) take into account the number of seats which a political party deserves to have under (2), deduct by number of all seats of the House of Representatives under constituency basis received by that political party in every constituency, the result is preliminary number of members of the House of Representatives under party list basis of that party;

(4) under provision (5) allocation of number of members of the House of Representatives under party list basis which political party may receive a total number of one hundred and fifty members by allocating for political party following result under (3) as integral number first, if one hundred and fifty members are still short, political party having fraction from calculation with highest votes shall be allocated with number of members of the House of Representatives for one additional member respectively until the total number of one hundred and fifty is fully allocated. In case of fractions from calculation are equal, proceeding under (6) shall apply;

(5) in case of a political party has already won seats of the House of Representatives under constituency basis equal to or higher than the number of seats which that party should receive under (2), that party shall acquire number of seats of members of the House of Representatives as won under constituency basis and not eligible to be allocated more seats from party list basis, leaving those remaining seats to be allocated for political parties of which the number of seats won lower than the figure they should get under (2) by pro rata but shall not cause to any political party as mentioned earlier to acquire seats exceeding the number it should enjoy under (2);

(6) having been allocated under (5) if it appears that the allocation of number of members of the House of Representatives under party list basis has not yet reached one hundred and fifty members, the political party with highest fraction from calculation shall be allocated with number of members of the House of Representatives under party list basis on more seat respectively until the one hundred and fifty members is reached. In case of the remainder of each political party is equal and allocation of member of the House of Representatives under party list basis to complete one hundred and fifty members is unable to be done, average votes of each political party for number of members of the House of Representatives which should have one member shall be considered for one seat more than other political parties, such political party shall be eligible to get one more seat of members of the House of Representatives, and if the average figures are still equal, drawing lot shall be applied;

(7) in the case where the calculation under (5) having appeared that all political parties received members of the House of Representatives under party list basis with total sum up more than one hundred and fifty members, calculation for adjustment of number of members of the House of Representatives under party list basis shall be done by following pro-rata accord which all parties should receive from allocation the number of members of the House of Representatives under party list basis altogether not more than one hundred and fifty members by taking number of members of the House of Representatives under party list basis which each political party may receive multiply by one hundred fifty, divided by additional result of one hundred and fifty with number of members of the House of Representatives under party list basis being exceeded one hundred and fifty, and provision under (4) shall be applied mutatis mutandis.

(8) upon the conclusion of the number of seats under party list basis of each political party being reached, candidates following their running number in the list of that party shall be elected members of the House of Representatives;

In case of a candidate dies after the closing of election application but before the closing of polling stations on polling day, votes cast for the dead candidate shall be accounted for under provision (1) and (2).

Proceeding under (1) to (8) shall be under prescription of the Commission.