The Ski Speeder is only available in Galactic Assault on Crait and can be used only by the Resistance. It requires 200 Battle Points to spawn in. Once the Ski Speeder is selected, it will spawn inside of a hangar and fly down to the planet's surface. It has considerably fast speed and can deal fairly heavy damage to the AT-M6's.
When The Last Jedi Season first released, the Ski Speeders were capable of accumulating thousands of Battle Points by firing on the AT-M6 walkers. Their point accumulation was significantly reduced in the 1.2 Patch, however.