Corby wore the ring on the fourth finger of her left hand, which is traditionally where engagement and wedding bands are worn.
One of her followers noticed the accessory and commented, "That's a beautiful ring you're wearing", alongside an engagement ring emoji.
Tellingly, Corby replied: "I think so too."
Corby and Panangian first met at a church service in Bali's Kerobokan Prison in 2006 while both serving sentences for drug-related crimes.
She has previously described Panangian, a former surfer who runs a stand-up paddleboard rental business in Bali, as her 'soulmate'.
In March, Corby told Woman's Day that the couple were "trying for a baby".
At the time, she claimed they were "hoping to become pregnant" while on holiday in Thailand. This trip eventually took place in April.
They only spend "two precious weeks a year together" because Panangian is unable to enter Australia due to his criminal record.
Corby can return to Indonesia if she chooses, but does not feel "comfortable" doing so yet. Instead, she and Panangian meet in countries where visas are not required for entry.
Corby, who hails from Tugun, Queensland, became a household name after she was arrested in October 2004 at Bali Airport with 4.1kg of marijuana wrapped in plastic inside her boogie board bag.
She was later sentenced to 20 years in prison, but after a series of sentence reductions was released on parole in February 2014 after nine years behind bars.
In May 2017, she was deported back to Australia amid a media frenzy.
Corby has always maintained her innocence, insisting the drugs were planted in her luggage by an unknown third party without her knowledge.
Last month, she re-released her 2006 prison memoir, My Story, co-authored by journalist Kathryn Bonella, in updated form with additional chapters.
