Question [Q] Turn on WiFi and Ping gets high Galaxy S3

Hi everyone, i had my galaxy S3 about 1year now, and just now i encounter this problem. So everytime i turn on wifi connection the ping goes more than 1000ms, and this is making the internet connection in my home sooo laggy.But when i turn it off (wifi on my S3) the ping goes smooth again just around 6-50ms. About a month ago i had the same problem and it's fixed by hard resetting my S3. But now this problem came again. I wonder if anyone here have the same problem, and have any suggestion how to fix this (not by hard reset/format factory i hope).

Thank you, I look forward for your reply