Would a thong lift aka inferior butt lift fix this after BBL? (Photos)

Dear HotChocolate23,
I understand your concern. However, without a proper assessment, it would be difficult to determine what went wrong. It is best that you visit your plastic surgeon for further assessment or ask for a second opinion. Only after a thorough examination, you can get proper recommendations and advice.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

Allow me to answer your question as best i can based upon your photos. However, please keep in mind that an in-person consultation with physical exam, or at least a virtual consultation, is first necessary before any legitimate evaluation or final surgical recommendations are made.
In general, cosmetic hip implants are the most reliable, predictable, and permanent option for filling in the hip dips and creating more of that feminine hourglass figure, whether slim or not. On the other hand, fat transfer to the hip area tends to survive quite poorly in most patients and thus produces only short term results (often less than 10-12 months). Injections/fillers such as Sculptra or hyaluronic acids are cost prohibitive (i.e. guaranteed to be the biggest waste of money of your entire lifetime), short lasting and possibly deadly with high volume injections. Others such as silicone/PMMA/hydrogels/etc are cheap but extremely dangerous and a personal commitment to a life of serious and sometimes deadly consequences. Typically hip implants are best custom designed and created for each individual patient’s anatomy. Because an extremely few number of board-certified plastic surgeons perform this procedure, make sure you seek consultation with a reputable and experienced cosmetic hip implant specialist. You may have to travel a long distance from home to find this particular surgeon. Glad to help.

No idea about doing a cutting lift. I recommend a round 2 lipo reduction of higher fat areas with fat added to hips and inferior dents. Fees from $8,000+.