Diana Stalteri, and Cheryl Wenninger - both from Perth, Australia - told BBC Wales they reportedly loaned the one-test All Black thousands after he pleaded for help with cash flow problems, but failed to pay them back.
King refused to comment when contacted by BBC Wales, but the 38-year-old did not deny the allegations. BBC Wales said there was no suggestion he had acted illegally.
Both Ms Stalteri and Ms Wenninger have messages and e-mails from King that show him admitting he owes them thousands of Australian dollars, which he promised to pay back.
Ms Stalteri, 40, said she met King online in late 2017, and he asked to borrow money after they'd been going out for several months.
She agreed to loan him A$10,000 (NZ$10,500) on the condition she could see his rugby contract and would pay it back. That never eventuated as she ended the relationship in May 2018.
"It was an immediate family member [of King's] that rang me with information about the money - that he had a gambling addiction, and the amount of money he owed people, particularly in New Zealand," Stalteri told BBC Wales.
"I just knew you wouldn't get a call like that from an immediate family member without it being somewhat true."
Ms Wenninger, 47, told BBC Wales that King appealed to her "compassionate side" by claiming that some of the thousands she loaned him was for his children.
"If I wasn't able to give him cash, he'd become quite distraught, quite emotional," she said.
"When I finally found out the truth, I contacted Regan... he told me he had a mental illness and he has been unwell for such a long time
"There are no divorce proceedings, no bank accounts, no assets and that was the premise for him to obtain money from me."
Ms Stalteri added she had spoken with five other women who claimed to have had similar experiences while in a relationship with Mr King.
BBC Wales as spoken independently to five women and two men, all of whom claim to have loaned Mr King without being repaid.
King, 28, recently left Welsh Premiership side Neath after playing for a number of clubs across Europe since 2004.
His playing future is uncertain, but Wales Online reports that Luxembourg is a possible destination, along with a return to New Zealand, where he played for Mid Canterbury in 2017.
The man from Cambridge is the brother of international squash star Joelle King.