Malaysia or Vietnam with my Thai Girlfriend and will she have issue at immigration due to language barrier?

I am currently in Thailand and planning around a 2 week trip with my Thai girlfriend. I know I want either Malaysia or Vietnam.

I am a lazy traveler and mainly want a relaxed beach - city trip with good food and comfortable vibes. Wake up late, eat, chill, relax and repeat.

Main thing I want advice on is weather and visa.

1. Since this will be in mid June, where would you go between places like Da Nang, Hoi An, Phu Quoc in Vietnam OR Penang, Langkawi in Malaysia by weather?

2. Since my girlfriend is Thai (she can't speak english fluently - just a few basic words), if I bring her with me (I have a visa exemption passport too, would immigration be an issue due to her language barrier? I don't want to give immigration any red flags like I am trafficking her.

Do advice ! Thank you.