The 22-time Grand Slam champion had arthroscopic surgery last June after injuring his left hip flexor during his second-round defeat by Mackenzie McDonald at the Australian Open in early 2023.
Nadal returned to competitive tennis in the new season on Sunday and crashed to a doubles defeat while partnering retired veteran Marc Lopez but showed glimpses of his top form ahead of the January 14-28 Melbourne Park major.
"Today is honestly an emotional and important day for me after probably one of the toughest years of my tennis career," Nadal said after his win.
"I had the chance to come back after a year and play in front of an amazing crowd and play at a very positive level on the first day is something that makes us feel proud - my team and family who have been there every day in the last year."
Nadal looked razor sharp again during his latest meeting with qualifier Thiem in a rematch of their 2018 and 2019 French Open finals which he won, as he ramped up the pressure and claimed the opening set with a break.
Roared on by fans inside a heaving Pat Rafter Arena, Nadal grabbed an early break in the second set with a superb backhand pass and barely looked back as he racked up a 5-1 lead before closing out the match on serve.
"I missed being healthy and feeling competitive, playing in front of full crowds that have been amazing all my career here in Australia," Nadal added.
"I can't thank everyone enough."
Nadal's 1,069th men's tour-level victory meant he surpassed Ivan Lendl to sit fourth in the all-time list.
"As you can imagine, today it wasn't a statistic I was aware of," Nadal said.
"I had enough work just to be focused and come back on court and remember how to play in a competitive match.
There were nerves and doubts before the match, but things went well and I'm excited to be back."
In the women's draw, Arina Rodionova overcame 2020 Australian Open winner Sofia Kenin 7-5, 7-6(7) while double Melbourne Park champion Victoria Azarenka beat Anna Kalinskaya 6-1, 7-6(8).
US Open holder Coco Gauff started her new season with a victory at the Auckland Classic as the 19-year-old defending champion beat fellow American Claire Liu 6-4, 6-2.
Gauff, who is looking to improve on last year's fourth-round finish at Melbourne Park, next plays world number 117 Brenda Fruhvirtova after the Czech 16-year-old defeated Anna Blinkova 7-5, 6-4.
Second seed Elina Svitolina eased to a 6-4, 6-3 victory over Caroline Wozniacki and next meets 2021 US Open champion Emma Raducanu who returned following wrist and ankle surgeries to beat Elena-Gabriela Ruse 6-3, 4-6, 7-5.
