Updated

The political movement that has won every Thai election in nearly two decades is facing its biggest test yet: Squaring off against the allies of the military junta that removed it from power and rewrote the electoral rules with the goal of ending those victories.

The latest public face of that movement, Pheu Thai party leader Sudarat Keyuraphan, warns that Sunday's vote won't be fair. Nevertheless, she is urging voters to turn out in force if they want to oust coup-maker and now Prime Minister Prayuth Chan-ocha.

She said: "We have to tell the people that it's the only day that we can stop Prayuth extending his power."

The vote will be the first since Prayuth led a military coup that toppled the Pheu Thai-led government in May 2014.