@Bobby *******
thank you for your advices, I contacted w Hua hin immigration office before I find a agent, they did ask the letter. I reckon if I go another immigration office they might not ask. When I enter in thailand I carried stv visa which requires a insurance, when the first time I extended my stv visa, Hua hin immigrants office told me my insurance is not on the list, I have to change a insurance, meanwhile I enter this country w it. Sometimes I doubt if they are in a same system.