The university student was pronounced dead at hospital after lifeguards dragged her from the water and performed CPR for 15 minutes.
A Thai legal source told AAP that "the bigger issue is clear, [it] is about the cause of the accident".
Police could charge Keating with reckless driving causing death, Fairfax Media reported today.
Keating's sister Bree Lyon told Fairfax his family was "absolutely devastated" about the death of "our darling girl" with a "beautiful smile".
Friends of Collie, who went Charles Sturt University, used social media to post tributes.
"Emily Jayne Collie you will forever be loved, hope there's a nice big trampoline up there for you xxxx," one woman wrote.
A Department of Foreign Affairs and Trade travel advisory warns there have been many serious accidents involving jet skis and motorcycles in Thailand. DFAT is providing consular assistance to Collie's family.
- AAP