No where in Thailand are you going to get them cashed without some type of service charge. My advise is to use your ATM card.
I don't know about commission free, the commission is only 33 baht no matter what the size is anyway. It has been that way for quite a few years. I imagine if some place cashed a travelers check without a commission your return would be less.
There are lots and lots of banks and small branch banks. On Beach Road, on Pattaya Second Road, on lots of main roads. At the Big C mall, at the Villa Market mall, outside the Lek Hotel, near the Royal Garden Mall. These banks give an honest return and are usually better than hotels and stores.
To cash the travelers check you will be asked for your passport and often what the name of your hotel is and room number.
So, no problem cashing travelers checks. Lots of ATM machines all over the place too!
I dont think you will get any reputable bank or foreign exchange to cash them commission free. Otherwise there are many exchange cabins all over Pattaya
