Where should I take my new Thai girlfriend for a vacation?

My Thai girlfriend and I want to travel outside of pattaya. She doesn’t travel at all and she has a passport. I told her we can go to Koh Chang or maybe somewhere outside of the country that’s affordable. I’ve always wanted to visit Cambodia but I’m not sure if that’s a good option, seeing as she is Thai and there is conflict. Does anyone have any experience or recommendations of where to go?