Hi folks
I am a Thai citizen. I concur with what other people have said above, in general the Thai police will leave innocent looking tourists alone, i.e. no search etc. The threat from terorists in the country is extremely low, so security measures like metal detection and body search in tourist places and public buildings are not usually carried out (except, of course, in your own embassies). And in that case, they are not after you tourists, anyway.
In general, SAK and muti-tools are acceptable in the view of the authority. But you better not ask them about the legality of knife carrying; like in many countries, knives, particularly fixed blades, are considered offensive weapons. I agree that you may need something other than multi-tools , but please be as discreet as possible if you are to pack medium to large sized folders with you. Avoid fights or aggrevating the wrong people, they do guns, not knives. The Thais are in general friendly, though. And you can get a lot of helps from the tourist police, they display clear badges of their branch on their vehicles.
One advice, SAK and muti-tools are very pricey in Thailand. You may be able to make some profits selling them to the locals or expratiates when you leave

0. Oh, I have another idea, why don't you pack a Cold Steel folder and the Spacial Project catalogue with you. Non-kinfe people should be very impressed with the hype and pay what you demand from them, he he. I'm in Britian right now. Wish I was in Bangkok, so that I could offer some helps when you're there.
TD