Why do Thai people have really long last names?

During the time when China mainland transformed their political system from a monarchy to communism, lots of Chinese left the country seeking a new life opportunity. Many of them selected Thailand as their destination. They started a new life in the Kingdom with prosperity. They still kept their identity by using their Chinese name. Thereafter, their kids, the following generation, were born with a Thai name. However, they still used a Chinese family name like Tang, Lim, Ng, etc. They then came to realise that it was not localized enough to have a Thai name with a Chinese last name. They began to apply for a Thai last name. That is the starting point of this story.

When you go to apply for Thai last name, the regulation for registration of the new last name is as follows:

1. The applicants submit 5 alternatives to the government officer. Each one has a maximum of 10 Thai character.
2. The officer will search in the database for identical last names. The law does allow identical last names to those existing already So hopefully, one of your 5 alternatives will be unique and can be used.
3. About one month later, you will check with the officer. If there is any duplication, you need to create the new one and resubmit it again. If not the case, you can use the real NEW last name. 

Since we have a lot of immigrant Chinese, subsequent applicants have to create a new name that has a low probability of duplication. Thus, the new surnames just get longer and longer.

Source: http://www.apmforum.com/columns/thai4.htm