i heard too many versions of people, some say if you did 90 days visa with koh samui extention ( i live in koh phangan), you get only 15 days in burma visa run.

some say 30 days...no problems...

who should i believe ? how can i check it ?

Land border crossings gove 15 days visa exempt entry. Flights in give 30 days visa exempt entries. Crossing a border will not give you a visa.

Call a local visa run service and tell them your details.

If you have a visa already, and you're just doing a border run. 30 days.

If you don't have a visa, or your visa is finished when you leave Thailand. 15 days.

By land.

If you are doing a border run with a valid visa for Thailand it would be the normal period allowed for that type of visa entry for your nationality. 30 days, 60 days, 90 days or one year.