Just my perspective, but having mentioned her sister and brother in law can continue to run the business in her absence was a mistake. It shows she does not need to return to Thailand to maintain her business and could remain in Canada. Bringing a lawyer into it is nearly pointless due to the fact foreign nationals really have no course to appeal an IRCC decision made under the pretense to protect Canadians from "Bad People".
When I brought my spouse from Indonesia, I spent a significant amount of time establishing a travel history prior to applying to Canada. It involved multiple trips to Singapore and a few trips to Australia. The Australian trips were key to establish credibility, as a visa is required and we made sure the trips were short (5-7 days) and that there was never an overstay. Make sure she has a reason to go back to Thailand! The visa officer at the Canadian Consulate in Jakarta told me one of the primary reason for a visa approval is that they are sure she was going to leave! I'd leave running the business out, as they already have the old applications stating her family can take care of that. Some family event, or school, etc....something tangible. Remember, she has to prove she can afford the trip first and foremost. You're financials and support are secondary considerations and there is nothing binding you to pay for anything. Estimate a $1000/week for a trip, not including airfare.
Ask for a week and a single entry visa. Show a timeline and plan a detailed trip (we said we were landing in Vancouver, driving to Alberta to meet my family and driving back, at which point she would fly out when I travelled to the US...I included my ticket). Showing your ties to Thailand might help, but others should comment on that. You have to remember that generally, they issue the visa with no specific entry date, just an expiry. The determination of how long she can stay is made by CBSA when she enters Canada, and even at that, it can be extended once she is here.
Don't be in a hurry to reapply, address the rejections they provided you first. Order the GCMS notes on the file for more details.
Best of luck