I have been looking in all the bigger malls but it seems to nearly impossible for me to find it by my self that's why I am asking for your help. I will also need the accessories for running.

Where to buy?

wow, not sure about that area, there is an apple reseller with the legit stuff at J Avenue on Thonglor, also see plenty at malls such as MBK.

hmm I dont know what you class as a 'major mall' but there are plenty of Apple retailers in BKK.

I have seen in all the following: Paragon, Discovery, MBK, Villa Center, J Avenue, The Mall, Fortune, Pantib, Esplanade so I cant imagine how you cant have come across one.

Doing a google search reveals the store locations : http://store.apple.com.au/asia/FMPro

You could also buy it online from Welcome to the Apple Store - Apple Store (Thailand)

I found the above in less than 2minutes using google, so in the future, instead of walking through all the major malls, you may try using the internet to speed up your search

There is are official apple stores in Thong Lo, The Silom Complex and Siam Paragon 3rd floor + almost every other department store or shopping centre will have almost an entire section devoted to Apple on their Tech floor