IM A THAI CITIZEN CAN I APPLY FOR A VISA FOR DURATION TIME 60 DAYS PER ENTRY ?

You can apply for a visa with 60 days duration of stay per entry, but the final decision is up to visa officer, if you just go to China for sightseeing, I guess you will be issued a single entry tourist visa with 30 days stay duration after entry. The round-trip flight tickets should be provided to prove that you want to stay in China for 60 days.