Tamils or Tamil People are from Tamil Nadu, a state in Southern part of India.
Tamil people are called Tamizhar in Tamil language or some times in English we refer as Tamilar or Tamilans.
Note the difference at the end of these two words: Tami"zhar" and Tami"lar".
We say, the beauty of Tamil language is in the last letter in the name of the language itself. The letter is "Zha". There is no equivalent pronounciation in English for the last letter in Tamil. Hence we use "il" or "izh" or "zhar" or "lar".
In India, Tamil people are living in Tamil Nadu and Pondicherry - a french town in India.
While Tamil tradition lives in the country side of Tamil Nadu and Pondicherry, there are Tamilians who are living in different countries globally strive to follow the tradition.
More about Tamils can be found in this wikipedia page.
Tamil cusine is famous in many countries as there are settlement of Tamils that happened few centuries ago. Because of several generations of Tamils living in some countries, they have recognized Tamil language as one of their National language. For example: Srilanka, Singapore, Malaysia.
Check out this page to learn more about Tamils around the globe.
While many Tamils may not be living in Thai and Cambodia, the influence of Tamil style cooking is visible through out their cuisine.
In Singapore and Malaysia, you can get several traditional green leaves which are rare to get in all parts of Tamil Nadu. And there are several generation of people in these countries who are born to Tamil line of parents but have not visited Tamil Nadu in their life.
Tamil cuisine is oldest in tradition and other South Indian cuisine has many similarities with Tamil cuisine. Some features prominent in other South Indian cuisine compared to Tamil cuisine are: more coconut is used in Kerala food, more spice or chilli is used in Andhra food and Karnataka food are little sweet. All are unique tasting cuisine.
In Tamil cuisine, we categorize taste into Six tastes of food that is unique in Tamil cuisine. If you have not heard about Tamil food earlier, then you will know only Five tastes of food.
The world sees India as the country that gave "Curry". The word "curry" was given to the world by Tamil. Yes "Curry" originated from the Tamil word "Kari". Check out this page to learn more Tamil culinary terms in English.