The soaking should help if the oedema is from any sort of toxicity. Which could have easily occurred from where it was shipped, during shipping, or where you purchased it. Soaking in spring water can also yield results. Bloated african clawed frogs can recover well with a soak in epsom salt. I would try soaking in spring water with epsom salt for a week or so to see if symptoms improve. Make sure the water is "frog warm" and try soaking for 30 minutes daily. A word of caution though, an oedema can also be a symptom of kidney failure, which unfortunately, there is no cure. Only time will tell, but I wish the best of luck to your pac man.