A lot depends on what you have to offer, but it's worth bearing in mind that a lot of the jobs are restricted to Thais. If you're a native speaker, teaching English is obviously a popular choice. There are some IT jobs taken by foreigners. It helps if you get transferred here by your company back home, so that's another way.

There is also work in hospitality (manager/director level upwards usually). This kind of job brings many foreigners to Thailand.

IT also have jobs, but I think too many people are wanting the same IT job, so very much competition.