Advanced voting is usually a tepid affair, but on Sunday excitement was high as voters turned up in droves to polling stations.
More than 2.3 million Thais are expected to vote before the official March 24 poll date.
Since a 2014 coup ousted then-premier Yingluck Shinawatra, the junta has repeatedly postponed democratic elections -- much to the chagrin of the Thai public.
"I finally have a chance to cast my vote as I've waited for so long," said 48-year-old Paka Kaengkhiew as she stood in line in front of Bangkok's Phra Khanong district office.
In Dusit district -- home to military offices and government buildings -- voters crowded in a school yard before a polling station there opened.
People dressed in their work clothes -- military uniforms, hospital scrubs and more casual attire -- waited patiently to cast their ballot, aided by student helpers.
At 9 am Prem Tinsulanonda, the powerful head of the Privy Council -- the advisory board to Thai King Maha Vajialongkon -- arrived at the school.
Watched by Thai and international media, the 98-year-old was pushed in a wheelchair into a classroom boasting a portrait of the late King Bhumibol, who he advised, before walking the final steps to a polling booth.
More than 51 million Thais are eligible to vote in the official March 24 election, which will be held under a new military-scripted constitution.
Analysts say the new electoral system favours the army-aligned party fronted by junta leader Prayut Chan-O-Cha, who is running to be civilian prime minister after a government is formed.
But voters on Sunday still held on to hopes for change.
"I vote today in the hope for better change," said Mart Bupa, 53.