I would like to express my sincere thanks to my thesis advisor, Miss.Catthida Chaiposri and Mr.Catchawan Ponkeaw.for help and constant encouragement throughout the course
of this research. I am most grateful for teaching and advice, not only the research
methodologies but also many other methodologies in life. I would not have achieved
this far and this thesis would not have been completed without all the support that I
have always received.