I am Thai lady...so I would like to recommend you that I am not sure about your relationship with your girlfriend so if you never be relationship with her in person so you maybe her ATM only and important reason that is your business..good luck... from USA... TransferWise, Money gram are good rate more than western union
Sorry for my recommendation to you...first you or her should find a place for her quarantine in Bangkok and I think it is easy or comfortable in your journey to stay in Bangkok together. Or if she quarantine in hotel of Bangkok already when she fight to Chiang Mai don't need to quarantine again but must go to report to office in Chiang Mai as governor of Chiang Mai made noticed that about covid-19 cases