Serious concerns have been raised by the discovery of barcodes and QR codes with unique numbers on ballot papers used in last weekend’s general election, potentially revealing how each voter cast their votes; this could lead to voiding the elections.

According to the Constitution, MPs shall be elected by “secret ballot”, and any identifiable marks shall not be placed on ballot papers.

On Thursday (12 February), the Election Commission of Thailand (ECT) stated that barcodes and QR codes were used for security reasons, and were used to identify which ballots belonged to which polling station, as a measure to track and safeguard ballot papers.

A reporter from PPTV experimented by scanning the barcode shown on ballot papers. The barcode for each ballot showed the different numbers. For example, ballot 1, marked for the People’s Party, displayed the barcode number A37805055, and ballot 2, marked for the Bhumjaithai Party, displayed A37804930.

Matichon observed that ballots for party-list MPs carry a barcode at the bottom, while ballots for constituency MPs contain QR codes both at the bottom and on the ballot stub. However, the ballots used for the referendum do not contain any barcodes or QR codes. In addition, no such barcodes were found on the ballot papers in the 2023 elections.

According to We Watch, Thai netizens have raised concerns that each ballot paper may be assigned a unique running number, as it was found that 20 ballot papers in each booklet carry different numbers. The number in each ballot also aligned with the one on its ballot stubs.

Each ballot paper could therefore be scanned to connect it to its ballot stub, voters where voters were required to sign their names on ballot stubs. The ballot stubs also contained the voters' numbers from the lists of eligible voters in each constituency. This makes it possible to identify which voter completed each ballot paper and which MPs or parties they voted for.

Although there is still no solid ground to prove that the data was used in a way that violates the principle of ballot secrecy, academics and the general public urged the ECT to disclose further details to restore public confidence in the electoral process.

On Friday (13 February), Prasit Puttamapadungsak, an MP candidate for the People’s Party, submitted a petition to the ECT, calling for an investigation into ballots carrying barcodes and QR codes. He argued that these codes had the potential to link ballot papers to ballot stubs, raising concerns about the possibility of tracing them back to individual voters.

He noted that the issue arose after members of his team, who have expertise in technology and artificial intelligence, noticed a barcode on the party list MP’ ballots. When they scanned one, they found that it corresponded to the number printed on the ballot stub.

It was also found that the constituency ballots and MPs’ ballots contain five-digit codes capable of generating more than 60 million data sets, sufficient to cover 52 million eligible voters.

Prasit observed that if such tracking is possible, the system may be used to allow those who bought votes to verify whether recipients complied as requested. He asserted that such a possibility could undermine democratic principles and potentially put voters’ privacy and safety at risk.

Prasit also remarked that he would submit the petition to the Ombudsman, for the case to be forwarded to the Constitutional Court for further deliberation on whether the election should be invalidated.

Meanwhile, Chusak Sirinil, Pheu Thai deputy leader, revealed that the party’s legal team is gathering evidence. He said that in the past, ballot papers carried only security codes indicating the polling station or constituency to which they were assigned, and they could not be used to identify individual voters.

He added that according to the law, elections could be invalidated on two principal grounds: failure to ensure a secret ballot, and failure to hold elections simultaneously nationwide.

On the same day (13 February) the ECT held a press conference regarding the barcodes and QR codes, citing the provision which allows it to prescribe codes or marks on ballot papers as a safeguard against “forgery”.

The barcodes were also used to track the polling stations where the ballots were distributed, and that would help prevent ghost voting and electoral fraud.

The ECT also asserted that tracking to identify individual voters is impossible. It said that doing so would require access to additional elements, including ballot stubs and voter name lists, which are now kept separately, and that the Commission could not verify whether the numbers on the barcodes align with the ballot stubs as requested by the media and general public.

When asked which occasions the ECT would scan barcodes, it said it would only do so if a complaint was filed, as the ECT must identify the polling station where an issue arose. The ECT admitted that the barcodes could trace back to the ballot stubs, reiterating that they were included for investigation and maintain transparency.

When asked why barcodes and QR codes were used and why different numbers appeared on each ballot, the ECT stated that this depended on the printers’ methodology, which could not be disclosed.