หมอนิกคะ There're different styles of graduation caps, hoods and gowns in Thailand. I think it's based on where lecturers graduated and what university policy applied. Colors on hood and gown are concentration of study or the color of the university. Besides, a number of stripe on the arm of the gown is different meaning too. For example, if you see 1 stripe on the arm. It means this is a bachelor degree graduation; 2 strips mean a master's degree graduate, and 3 strips is a doctoral degree. Some place's applied the gown from British system. All graduate covers entire body with gown without stripe and wears big cap. However, in some university (like my American university) there is no strip, just a gown with a robe for the bachelor graduate. The master's degree gown has longer, closed sleeves and no stripe. While the doctoral gown usually made of velvet, has 3 stripes on the arms, and includes a hood.