Millions of Thais headed to the polls on Sunday for a general election where opposition parties are hoping to ride a wave of frustration over the military's stranglehold on the levers of power and its handling of the economy. The election is the first since youth-led mass pro-democracy protests in 2020 and only the second since a military coup in 2014 ousted an elected government, restoring a conservative clique that has pulled the strings in the kingdom's turbulent politics for decades. Some 50 million Thais are thought to have turned out to elect 500 members to the House of Representatives in Thailand's bicameral system which was heavily rejigged through a new constitution written by the military that seized power nine years ago. Each voter has two ballots, one for a local constituency representative and one for their pick of candidates for the national party, known as party-list MPs. The junta-era constitution gives the establishment-dominated upper house a significant say in who can ultimately form a government so opposition parties must win by a strong margin. Leading that charge is a young generation of Thais yearning for change and willing to tackle taboo topics such as the military's role and even, for some of them, royal reform. "I want to see Thailand move forward," first-time voter Nichapa Yotpradab, 21, told CNN after casting her vote in the capital Bangkok. She added that she had been closely following the election campaigns and would be eagerly awaiting the results. Photos taken at various locations in Bangkok showed queues of people lining up outdoors to vote, despite building heat. "I want to see Thailand develop into a good way, I want to see good people in power," said Suratiya Suwanwihok, 59. "I don't want to see corrupt ones in power." The country's powerful conservative establishment is relying on its own influential voter base that supports parties connected to the military, monarchy and the ruling elites, many of them in Bangkok. Lined against them are more progressive and populist leaning opposition parties campaigning for democratic reforms that have a history of attracting more working class voters in the city and rural regions as well as a new generation of politically awakened young people. Topping opinion polls is the opposition Pheu Thai party which is fielding three candidates for prime minister and campaigning on a populist platform that includes raising the minimum wage, welfare cash handouts and keeping the military out of politics. It's the party of the billionaire Shinawatra family — a controversial political dynasty headed by former Prime Minister Thaksin Shinawatra. Thaksin, a former policeman turned billionaire telecoms tycoon, and his sister Yingluck ran governments that were ousted in military coups. Both also live in exile, with Thai courts sentencing them to prison on corruption charges in their absence. Thaksin's youngest daughter, 36-year-old Paetongtarn is standing as a prime ministerial candidate. Paetongtarn only entered politics three years ago but has presented herself as hailing from a new generation to connect with young Thais. She regularly attended rallies while pregnant and went back to campaigning days after giving birth. Enormously popular among the rural and urban working classes, the party is aiming for a landslide victory. Parties associated with Thaksin have won every Thai election since 2001. "I think people need change of course, they will come out no matter the weather; they are out and they want to use their rights," Paetongtarn told reporters after she voted on Sunday. "I think everyone should notice this and it is very important for them." Also in the mix for Pheu Thai is Srettha Thavisin, a 59-year-old real estate tycoon who wants to focus on fixing income inequality, promoting LGBTQ+ rights including same-sex marriage and rooting out corruption while boosting the sluggish economy. Speaking to CNN after casting his vote, Srettha encouraged "all Thais, as many as possible, to use their rights and come out to vote." He added that he would be watching the counting process later in the day at the party's headquarters in Bangkok. Another opposition force at play is the Move Forward party — hugely popular among young Thais for its radical reform agenda. Analysts have called it "a game changer" — its candidates are campaigning on deep structural changes to how Thailand is run, including reforms to the military and the kingdom's strict lese majeste law — which prohibits criticism of the royal family and makes any open debate about its role fraught with risk. Heading the party is Pita Limcharoenrat, 42, a Harvard alumni with a background in business. His eloquent campaign speeches and reform platform have earned him a massive following and he is one of the top picks for prime minister in opinion polls. Gunning for the top job is incumbent Prime Minister Prayut Chan-o-cha – this time with a new political party, the United Thai Nation. The former army chief who masterminded the 2014 coup has now been in power for nine years. Prayut arrived at a polling station in Bangkok with an entourage to cast his vote on Sunday. While his party lost out to Pheu Thai in the number of seats won in the 2019 election, Prayut still became Prime Minister after gathering enough support from coalition parties to form a government. But despite his poor performance in opinion polls, analysts have cautioned against underestimating him given his links to the country's elites. His rise from military coup leader to prime minister has been marred with controversy, growing authoritarianism and widening inequality. Hundreds of activists have been arrested during his leadership under draconian laws such as sedition or lese majeste. His military government's mismanagement in handling of the coronavirus pandemic and economy also amplified calls for Prayut to step down and continued well into 2021. He survived several no-confidence votes in parliament during his term which attempted to remove him from power. If elected again, Prayut can only serve two years as the constitution limits a term in office to a maximum eight years. Another candidate who could see his fortunes rise in any post-election wrangling is former army chief Prawit Wongsuwan, first deputy prime minister and former brother in arms with Prayut. Prawit, a political veteran, is now leader of Prayut's old party Palang Pracharat. The Bhumjaithai party's Anutin Charnvirakul could also prove influential in any post-election deals. Health Minister Anutin steered the country through the pandemic and was behind landmark legislation that decriminalized cannabis in the country last year. The head of the biggest party may not necessarily lead Thailand, or even form a government, because the country's electoral system is heavily weighted in favor of the conservative establishment. Parties winning more than 25 seats can nominate their candidate for prime minister. Those candidates will be put to a vote, with the whole 750-seat bicameral legislature voting. To be prime minister, a candidate must have a majority in both houses – or at least 375 votes. However, the 250-seat member Senate is likely to play a key role in deciding the next government of Thailand and, because it is chosen entirely by the military, it will likely vote for a pro-military party. That means an opposition party or coalition need almost three times as many votes in the lower house as a military party to be able to elect the next leader. Polls are scheduled to close at 5 p.m. Bangkok time (6 a.m. ET) and vote counting will begin shortly after. Observers say that early results can be expected at midnight in Bangkok – but it could be weeks or even months until Thailand sees a new prime minister. — CNN