Can my girlfriend repeatedly enter Thailand on a tourist visa every few months?

Hi all. Need your wise advice for my girlfriend. I am working for at least 2 years in Bangkok and she will come soon from France. She will apply for a tourist visa and maybe extension. So after 2 or 3 months, we will go on vacation outside Thailand in Asia. Then, she will apply again for a tourist visa from the country we will visit (+1 month extention) to re-enter in Bangkok. My question is : can she do that? ( I think so ) and more importantly, can she do that repeatedly every 2-3 months (by air) during my 2 years here in Bangkok? I am afraid that in the airport, the customs will refuse the entry if she do that too often (4-6 re-entry per year)

Thank you all !!