Bastia airport lounge searches deserve an honest answer up front: Bastia Poretta Airport (BIA), the main gateway to northern Corsica, is a small, seasonal regional airport, and dedicated lounge provision here is limited compared with a major hub. If you are picturing a large Priority Pass style lounge, temper that expectation before you fly.
Regional airports of Bastia's size often have little or no general-access lounge, and where any premium space exists, it tends to be tied to a specific airline's premium-cabin or elite-status passengers rather than open to the public or to lounge-network members. Rather than name a specific facility that may or may not currently operate, the honest guidance is to check directly with your airline for Bastia before you travel, since regional lounge arrangements can open, close, or change eligibility with little notice.
Priority Pass and major credit-card lounge programs are not a reliable bet at an airport this size. Coverage at small regional airports is inconsistent, and Bastia should not be assumed to have Priority Pass access simply because larger airports elsewhere do. If lounge access matters to you on this route, your best chance is a premium fare or elite status with the specific airline operating your flight, confirmed directly with that airline rather than assumed from a general membership.
Because Bastia is compact and seasonal, with traffic that swells heavily in the summer holiday months, the realistic plan for most travellers is to use the airport's general seating and food and drink options after security rather than count on a lounge. Arrive with a little extra time during peak summer waves, when the terminal is busier and queues can build. If you do hold airline premium status, contact that airline ahead of your trip to confirm whether any lounge or fast-track arrangement currently applies at Bastia, since this is the kind of detail that changes season to season at smaller French regional airports.