Why u think they give u that and beside u think they give u that maybe u can think yourself u not get it because u can go back to uk and when not have legal visa to stay than u have to leA e
I know manny successful foreigner with small and medium sice busines there are posibility for the smart thinkers, the monkeys and alcoholic they loose yes
Try to find legal service your wife in Thailand can find someone for u and u talk directly to them they help u from the first step and advice u in how to do , there many rules but also mammy ways to do or make busines and all the rules and ways depending on what kind of business
U have to go to the local Thai embassy they give u the only answer If u may enter its highly unthinkable when not have married, children , workpermit than can forget it ,but like I say only the thai embassy give u the right answer
U can leave the country but not can come back so visa run not possible, and I not understand your question u say u teacher and u have workplace than I think u have workpermit allready ?