How can I avoid gaining weight in Thailand?

Every time I have moved overseas for work in the past I have gained heaps of weight. Once I gained 30kg in 4 months, once 20kg in 5 months and so on. I finally lost all my travel weight and now weigh 62kg for 166cm height (I'm female). I'm moving to Thailand for six months and I am petrified that I will gain weight again, because I won't be able to eat salads etc. What do I dooooo????