GM cars are towable with the 4T40 automatic, from approximately 1995-2005. Includes Chevy Cavalier, Pontiac Sunfire, Oldsmobile Alero compact cars, and mid-size Saturn L, Chevy Malibu, Pontiac GrandAm, Olds Cutlass.
GM cars are towable with the 4T45 automatic, 2005-2010. Includes Chevy Cobalt, HHR and Malibu, Pontiac GrandAm and G6, Saturn Ion and Vue.
Note for these compact and mid-size GM cars I specify the transmission, because you may find special models, mid-size particularly, with performance options that matched more powerful engines with different GM or third-party automatics.
Compact SUV sold as Pontiac Vibe is NOT flat towable as an automatic, because it is not on a GM platform. It is on a Toyota platform, and Toyota doesn't want any of its automatic transmission cars being towed.
There are larger, heavier GM cars from the same era that can be flat towed, particularly the Equinox/Torrent SUVs, and the later Saturn Vue on the same platform. I'm not sure which transmissions were used, so can't cross-reference to other cars. I'm also not sure of cutoff dates, i.e. just when for a particular model GM switched to newer transmissions.
A lot of Saturns get towed. The 1991-2002 S-series, three generations, initially used automatics (MP6, MP7) unique to Saturn. This made Saturns towable a few years before other GM compacts got a towable automatic. Saturn L, Vue and Ion got the corporate 4T40/4T45 transmissions, and at the end became platform shares with Chevrolet models.
Honda CR-Vs are also popular towable automatics, 1995 through 2014. While the CR-V is a platform share with Civic and Element, and shared essentially the same automatic transmission with Accord, Odyssey and Pilot (as well as a number of Acura models), Honda at some point after settling a class-action awarding extension of warranty on the automatic, decided to say only the CR-V was recommended for flat towing. CR-Vs are about 3400-3600 pounds and a bit tall, yet they tow quite well.
Something lighter from Honda, the Honda Fit from 2002 to 2013 was flat-towable with the 5-speed automatic, North American versions. I tow a Fit, as it is about 800 pounds lighter than a CR-V and the amount of space works well for me. At 35 MPG over the past 20,000 miles it has been economical on fuel, but not so cheap on service from the Honda dealer. Mine happens to be the 5-speed manual, but that's my choice, not a towing necessity.
Honda Fit would be the closest package size to your Kia Soul.
There have been a number of Ford compact and mid-size sedans and SUVs that can be flat towed with automatic transmissions. I haven't kept track of the changes over the past several years, not since buying the Honda Fit in 2012.
