The 29-year-old is one of four former New Zealand and Australian internationals who will represent the kingdom in next weekend's final Olympic Sevens Repechage tournament in Monaco.
The others are former Wallabies forward Lopeti Timani, ex Australian sevens international Afusipa Taumoepeau and Tasman winger Tima Fainga'anuku, who is a former New Zealand sevens representative.
Fekitoa will link up with the Tonga sevens squad already in Monaco after playing in Wasps' final English Premiership match against Leicester Tigers this weekend.
The former Auckland and Highlanders star, who was born on Hihifo in the Ha'apai Islands, made his test debut in 2014 and played the last of his 24 tests for New Zealand against the British and Irish Lions four years ago.
He represented Tonga in sevens before moving to New Zealand as a 17-year-old, after earning a scholarship to Wesley College.
Players can switch their international allegiance by playing in an Olympic qualifying event, provided they have a passport for the second country and have completed a stand down period of three years.
By playing in 50 percent of Tonga's matches at the Olympic qualifying tournament in Monaco, Fekitoa will become eligible to play for the 'Ikale Tahi national team.
However, a mouth-watering debut against the All Blacks in Auckland next month is a no-go, with a test debut pencilled in for November.
Global travel restrictions, which include a lack of available places in New Zealand's Managed Isolation Quarantine facilities, means Fekitoa will not be available for the 'Ikale Tahi's July tests against New Zealand and Samoa.
RNZ Pacific understands two-test All Black halfback Augustine Pulu had also been keen to represent Tonga but did not complete the required paperwork in time.
Tonga internationals Cooper Vuna, Atieli Pakalani, Nafi Tuitivake and Sam Vaka, as well as Manu Samoa international Tim Nanai-Williams have all previously utilised the Olympic loophole to switch their international allegiance from Australia and New Zealand to represent their Pacific heritage.
Extended Tonga sevens squad for Monaco:
Fotu Lokotui, Jack Ram, Alaska Taufa, Roy Lolesio, David Halaifonua, Saia Fekitoa, Afusipa Taumoepeau, Malakai Fekitoa, Daniel Kilioni, Atunaisa Manu, Lotima Fainga'anuku, Vaea Vaea, Lopeti Timani, Ofa Fono, Violeti Kolo, Sunita Palu Fihaki.
