Im going to China in march and i want to bring back a cash register for my friends bar, I was told that China has a free trade agreement with Thailand, so would i have any duties to pay ?.

Last year i went there and came back with a laser disco light for my friends bar and customs charged me 3500 baht for it.

The light didn't even cost that much, I was pulled over and searched and the customs guy told me to pay him. I refused so he took me to higher ranking customs officer and he insisted that i pay him right in front of the airport cameras, put it in his pocket and told me to go away,

When i asked him for a receipt he got very nasty with me. So i thought it was best to leave it.

Might do better in the business forum.

I would think that FTA terms would apply to Thai companies doing formal imports/exports to those countries. Stuff that you as an individual carry into the country in your hand luggage is a totally different matter.

You may save on some local taxes and duties by buying in China, but a cash register is certainly not a personal use item, so you are highly likely to be stopped again at customs. Surely the price difference locally is not that much?

I think you will be liable to pay import duty and tax on the cash register. If you were moving here as a non-thai resident and had a work permit then you could qualify for importing your personal and/or household effects free of duty/tax but that unfortunately is not the case. I would buy the machine here and save myself the hassle.