APIを使えば簡単にできます。
#uselib "kernel32"
#func WritePrivateProfileString "WritePrivateProfileStringA" sptr, sptr, sptr, sptr
#cfunc GetPrivateProfileInt "GetPrivateProfileIntA" sptr, sptr, sptr, sptr
#cfunc GetPrivateProfileString "GetPrivateProfileStringA" sptr, sptr, sptr, sptr, sptr, sptr
// ini書き込み
WritePrivateProfileString "Section", "Int", str(100), "Test.ini"
WritePrivateProfileString "Section", "String", "Test", "Test.ini"
// ini読み込み
ret = GetPrivateProfileInt("Section", "Int", 0, "Test.ini")
mes "Int=" + ret
sdim key, 64
ret = GetPrivateProfileString("Section", "String", "", varptr(key), 64, "Test.ini")
mes "String=" + key
stop