Gavin Green overcame a back nine stumble to card an opening 64 and set the clubhouse target on day one of the 2020 Saudi International powered by SoftBank Investment Advisers.
The Malaysian earned his place on the European Tour by winning the Asian Tour Order of Merit in 2017 and has been a picture of consistency ever since, taking his tally of top tens to six.
After three top 30 finishes on the 2020 Race to Dubai so far, he was once again showing his quality at Royal Greens Golf and Country Club, moving to six under.
Green got off to a flying start in the desert, turning in 30 with birdies on the first, fourth, sixth, eighth and ninth after going out in the first group of the day.
Another gain on the tenth made it a hat-trick but bogeys on the 12th and 14th brought him back towards the pack.
A stunning tee shot to two feet on the par three 16th got him back on track and when he put an approach to eight feet on the 17th, he led by two.
Stenson birdied the tenth but gave the shot back on the 12th before making gains on the 15th, 17th, first and third, with an up-and-down on the par five fourth seeing him trim the lead.
Soderberg - who last week played the fastest round in European Tour history at 97 minutes - was the next man to get to five under, picking up shots on the first, seventh, tenth, 12th, 15th and 16th and bogeying the third.
Arnaus is looking for a first victory after three runner up finishes in his rookie campaign last season and a tie for third last week, and he birdied the 12th and 15th but turned in level par after dropping shots on the 16th and 17th.
Gains on the first, fourth, fifth, seventh and eighth then sent him flying up the leaderboard.