Thailand was "colonized" by Chinese 1600 years ago. Those same Chinese are still pretty much in charge.
I have to say that the Chinese in Malaysia, Indonesia and Thailand do so well because they work hard and focus on business. The natives are less enthusiastic and rely on preferential laws, affirmative action and sheer numbers to get ahead.
Well, yes and no. Chinese had very strong influence in Thailand, and the states which are now known as Thailand, up until the mid 1800s when China lost the Opium War. Thailand realized the balance of power in Asia was changing and at that point started to break ties with China and develop stronger ties with the British, Dutch, and others. Without looking it up, I believe that this was under the reign of King Rama IV.
Chinese once again started to have influence in the 1970s with the closing of the US involvement in the Vietnam War. Of course, Toxin has taken this to a new level.