觉得 คิดว่า นึกว่า 感到 รู้สึกว่า ...

ช่วย means to help, it is the most common and casual way to ask someone to do something. ex. ช่วยด้วย! ... Help! (In case of emergency) ช่วยหยิบหนังสือให้ฉันหน่อย ... Pick that book for me (please). เชิญ means to invite someone to do something or to do as one pleases. ex. เชิญชิมฟรี ... Free (food) sample. เชิญตามสบาย ... Do as you please/Please make yourself at home. กรุณา means "please" in more imperative way, it is usually used to give out command or order. ex. กรุณารักษาความสะอาด ... Please keep it clean. กรุณาปิดมือถือ ... Please turn off your cellphone. Hope it helps :)

ชุดแต่งงาน

If you live downtown you can go to Kinokuniya at Siam Paragon on the 3rd Floor. There, you can find a lot of books, not only Thai, but also English, Chinese, and Japanese books. And they have the computer for you to find a book you want. It's very big so you might have to take your time to look around.

Both shared the same meaning, "old." But they were used for different purposes. "เก่า" will be used when ... 1. you describe how old something is (but you can' say "He is so เก่า," because that is so wrong.). You can only describe a subject, for example: ของเก่า (which means antiques). "เดิม" will be used when ... 1. you want to describe the oldness of someone or something, in a sense of how familiar it is to you. I can make an example as shown: เจอกันที่เดิม means Let's meet at the same old place (it implies that you and your friends have met at that place before.). Or it could be ไปที่ไหนก็เจอแต่คนหน้าเดิมๆ means Everywhere I go, I only see the old faces (it implies that there are nothing new. It was as usual. No one new. No excitement in life. Bored.) Hope those explanation helps. :)