Bryony Freestone, 19, from Little Houghton, Northampton, died off the island of Koh Chang on 14 August.
Her twin sister Sophie posted a picture of the pair on Facebook, captioned: "There's nothing I wouldn't give to have you back".
The University of Exeter, where Miss Freestone was a student, said it was "deeply saddened by this awful news".
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"Bryony is remembered as a talented, dedicated and hugely popular student and our heartfelt condolences and thoughts are with her family and friends," a spokesman said of Miss Freestone, who studied at Penryn Campus in Cornwall.
The Foreign Office confirmed it was supporting the family of a British national "who sadly died in Thailand on 14 August".
Tributes have been paid to a "talented, dedicated and hugely popular student" who drowned in Thailand.