The 56-year-old Belgian left Charlton when his contract expired at the end of the season.
He had only been in charge at The Valley since March but managed to save the club from relegation from the Championship with three wins in their final four games.
Blackpool have been without a manager since Barry Ferguson left his role as caretaker-boss, which he took on following Paul Ince’s departure in January, at the end of the season.
Seasiders chairman Karl Oyston has been speaking to a number of candidates for the job but he now appears to have decided on Riga.
Sky Sports understands that talks began over the weekend and that Blackpool are confident a deal will soon be announced.
Billy Davies and Brian McDermott were also reportedly in the frame, while Brian Flynn, Paul Hart, Ricardo Moniz, Paul Cox and Jackie McNamara have also been linked with the position in recent weeks.