I will be coming to Thailand in May and would like to know if I can bring my prescribed medication with me and what I need to bring with me as proof its given to me by my doctor? 

You can bring 30 day supply but nobody is going to check if it's 30/60/90 days for sure anyway. If it's something that's restricted in Thailand (psychotropic) etc, can't hurt to bring a copy of your scrip just in case. If you post the medication(s) you are concerned about, folks here can give a more definitive answer.

As above, state the name of the medication. With certain controlled substances (mainly narcotics) you need to get a permit in advance. With others all that is needed is a labelled prescription bottle. Though it is always good to have a brief doctor's summary of any chronic heath problem you have/meds you take in case you need to see a doctor while here.

Ive brought up to 6 months ,but i do bring a doctors scrip ,never had a problem in 15 yrs .

Thank you all for your help.