Can you tell me if i got inappropriately questioned and checked at the Los Angeles airport?

Whilst it may seem irregular, I would imagine that they have been tasked with targeting a number of unknown individuals. I agree with other comments that they probably used different wording to these questions, and they are really just asking the purpose of your visit. Thailand and other countries in that region have poor drugs trafficking records, and the use of drug mules (tempted tourists) is a real problem.