I booked the ThaiVietJet flight from Chiangmai to Bangkok. Their booking system allowed me to put only 2 letters for my fullname. After booking, I rechecked with the airline if they would let me check in, the answer is "No". I have already reported their behavior to Office of The consumer protection board of Thailand to prevent the this scamming practices.
Albeit their own mistake, they asked me to pay 240Yuan extra for name change.
I must say that before the company was renamed as trip.com they were Ctrip.com which run the business more ethically.
You have to stay away from this agency.