Jason Day has exploded to life on the back nine to nab a share of second, just one stroke off the pace, after the first round at the PGA Tour at The Sentry in Hawaii.

Australia's No.1 was labouring along at level with the card through six holes before collecting six birdies and an eagle to wind up with an eight-under-par 65 start to the new year.

Only American Sahith Theegala bettered Day with a 64, capped by his 10th birdie of the day at the par-5 18th hole that edged him clear of the field.

A last-start winner alongside New Zealand's Lydia Ko at an unofficial teams' event in December, Day is in a five-way tie for second in the 59-man field made up of winners from 2023 and anyone finishing in the top 50 in last season's FedEx Cup.

"It's a good way to start the year," the resurgent former world No.1 said of his first appearance at the elite event since 2019.

"I just can't help but feel thankful to be able to play this game and be here healthy and enjoying golf.

"I still want to compete and play well and try and win this tournament."

American Collin Morikawa also opened with a 65, as did Norwegian star Viktor Hovland, Korea's Sungjae Im and Colombia's Camilo Villegas, with world No.1 Scottie Scheffler in a bunch one stroke further back at seven under.

Morikawa has a special connection with the area, which was ravaged by deadly fires last year that killed at least 100 people.

The dual major winner, whose grandparents were born in Lahaina and had a restaurant in the town, has been volunteering his time to help Maui families displaced by the fires.

"Some weeks mean more than others, but when you have a connection like I do this week it's always going to mean more," he said.

The Sentry is the first of eight $US20 million ($A30 million) signature events on the PGA Tour schedule for 2024.

- with AP