The Samoan full-back has scored six tries in 19 appearances following his arrival at Franklin's Gardens just over 12 months ago.
That form has now been rewarded in the shape of fresh terms ahead of the 2016-17 campaign.
"Ahsee has been a good player for us over the past year and we're delighted that he's agreed to stay with us," director of rugby Jim Mallinder told the club's official website.
"His performance in Glasgow - when he scored two tries - springs to mind, while he also impressed in the first half at Exeter recently. Those kind of displays have helped make him an important part of our squad."
Tuala has been capped once by Samoa at senior international level.