C# application, problem with thai language on Windows ME

Question

i write c# windows application with VS .NET 2003 on Windows XP Pro SP2
when i run the application on windows XP
everything fine .... it can show thai language correctly.

but when i install the application on Windows ME
(with .NET Framework 1.1 Service Pack 1 & MDAC 2.8)
it also can show thai language
but except for the text in combobox and text in datatimePicker.
the text in comboBox and dateTimePicker appear as "unknow language" (alien language haha)

why ?
any solution to solve this problem ?

For the font i used when i write the application is MS Sans Serrif (the font support thai language)

thank you in advance ...