Language thinking problem in home Country?

I once had a Scandinavian roommate in the US who slowly forgot her native tongue and had trouble communicating with her family back in Finland. So this does tend to happen.

Nothing to worry about, really. If you wanted to reduce the impact of adjustment, use English on occasion in your SE Asian country, e.g pick up English language books to read, or watch some youtubes or movie DVDs from time to time.

Likewise, while in US, do use your other language - again, reading some books, watching some youtubes, phone/Skype calls back to friends & family in SE Asia, etc.

You're not quite fully bililngual, bicultural. This leads to a bit of a lag in being able to switch from one language & culture to the other. It's called code-switching. You are fluent in your languages, but not fully able to code-switch appropriately. Easily rectified.

a) Working overseas in Southeast Asia you may be more accustomed to hearing other languahes (French, Cambodian, Vietnamese, Lao, Cantonese Chinese, Taechow Chinese etc). Also, you may be exposed to "British English" with correct spelling, punctuation, definitions and meanings of words.

b) As an Australian, it is not the language that bothered me, but the cultural shock when I returned back to Australia from SE Asia. I felt uncomfortable on "Western society" as I had adopted more of an Asian attitude and customs as the "norm". I actively sought out Cambodians in Australia to be more at ease.

jeog-eodo. naneun eon-eoleul aju swibge bakkul su-issda.

Not in the least. I can switch languages very easily.