If they wanted to cause problems they could say you obtained the visa based in their company documents and now you wont stay. It obviously cost them money to change the visa and do the application. If they used an agent to so the process then probably around
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baht in fees etc. If they have their own HR and did themselves then maybe 1700 plus some time etc. I dont think they can cancel the visa now but obviously they are probably pissed off at the cost and waste of time.