Having come to this part of the world for several years now, I'm getting a better picture of the complexities of Thailand and to a certain extent Vietnam, Cambodia, Burma and Laos. The last two are next on my travel bucket list. The migration patterns in this part of the world is directly connected to cost of living, wages and other existential factors. The place of women is also problematic, as there are pressures on women both from the society and Western colonialist expectations of SE Asian women and girls.
The trafficking of labor in Asia seems to be widespread. Many voluntarily go for the sake of a job, but sometimes their handlers have a different agenda. Burmese, Cambodian and Laotian labor is very evident in Thailand. Your construction worker is often Burmese. The food service worker might be Khmer. Filipinos dominate the musicians in Thailand, since they speak English and can cover Hotel California without a problem.
In addition, due to ASEAN, there is a clear uptick in movements of transgender populations to Thailand. Unfortunately for the Thai Katoey, some of these new populations speak English much better, and might undercut their situation. However we look at the tolerance in Thailand for LGBT populations, some disproportionately end up in sex related industries.
What is unusual about illegal labor in Thailand is that they don't label the population necessarily in a negative manner. When you say illegal in America, it is automatically Mexican with a negative tone. You don't see this in Thailand, but there is clear exploitation of the population. Sometimes they earn 100 baht less than the equivalent Thai worker.
Women seem to be especially vulnerable. With the Rohingya, being refugees introduces opportunities for forced marriage. The trafficking of women seems to be going out of Thailand. Thai women are being shipped to various places like China. South Korean matchmakers are hooking up Vietnamese women with Korean men, and they end up beaten and abused. Basically, it's a front door version of trafficking. You don't hear about Laos, but I suspect it is happening there, as Thailand is cracking down. Sporadically, you see reports of shady Westerners molesting children in Laos. Lately, I view this sort of stuff as latent colonialism with a pervert's twist.
Why? It seems to be multiple vectors. Much of it would be market related and pay. Although Thailand doesn't pay like the US, they pay better than in Cambodia. Some of the refugee issues are triggered by religious conflict, but a lot of it is just plain socio-economics. With the ASEAN Economic zone, we might see more migrations of labor pools cross borders. Infrastructure build up is going crazy in Thailand, so there is a growth market here in construction labor. But with growth, there is a darker side to it. If you want a US example, look at what is happening in the fracking fields of North America. In the case of women, they are subject to the winds of international problems, and often they get a bad deal.