Taxis refusing to use their meters happens sometimes in Bangkok too. I had one pick me up, and tell me it was 100 baht minimum charge as he drove off. I told him no meter 35 baht minimum. He argued with me for 2 – 3 miles before turning on. So I got the first 2 miles free that day.
Bangkok is a safe place, and I never felt threatened, or in danger, but you do need to be street smart.
Never tell anybody that it is your first time there. Always say you have been there many times, and have many friends that live there when asked.