Is it possible to founder a thin horse?

i just bought a 16.2 hand gelding that's been out on a dry lot. he's been getting round baled gr hay, but the rest of the herd ran him off a lot. i'm having him delivered this weekend to my barn. there is lush green gr in all of my pastures. how should i go about turning him out? is it possible to founder an underweight horse this time of year if i just put him out on pasture from around 5 pm until 6 am?