Thank you Dr Ple : You give me another chance to talk about character encoding (TIS 620, MS code page 874, ISO/IEC 8859, Unicode and UTF-8 -- stuff like that ;-). Thailand's standard encoding is the TIS-620, but a number of government websites still carrying on with Microsoft's propriety codepage 874 --shame, shame, shame--. Unicodes have been to allow multiple character sets/languages in one document. The Internet has now adopted UTF-8 (which is a shorthand codeset for some millions unicode characters).

Why Unicode or UTF-8? 

1) document unterchange (partners in AEC); TIS-620 and MS-874 only encode Thai and English but not other character sets in AEC.

2) UTF-8 is preferred on the Internet; the Internet is "the" most used infrastructure for communications; compliance to Internet makes sense and better use of standardised resources;

3) MS-874 is being phased out and replaced by Unicode16/32 on Windows 7 & 8.1 conversion to UTF-8 from Unicode16/32 and TIS-620 is by computation and hence less costly than from MS-874 where table look-up is required.

UTF-8 is a more compact format for unicode --saving space/size-- and can be converted to Unicode16/32 efficiently.

What do we do with old documents coded in MS-874?

For archive purposes: just store them as they are;

For reference purposes (frequent retrival): convert them to UTF-8 (using LibreIffice or OpenOffice or MSOffice)

For use as forms: convert them to UTF-8 and save as Master documents; convert from the Master ducuments to PDF for public use.

There is no excuse for not creating new documents or saving recieved documents in UTF-8. Absolutely!

Here is what Wikipedia says:

The Microsoft Windows code page 874 as well as the code page used in the Thai version of the Apple Macintosh, MacThai, are extensions of TIS-620 — incompatible with each other, however.

UTF-8 (UCS Transformation Format—8-bit[1]) is a variable-width encoding that can represent every character in the Unicode character set. It was designed for backward compatibility with ASCII and to avoid the complications of endianness and byte order marks in UTF-16 and UTF-32.

UTF-8 has become the dominant character encoding for the World Wide Web, accounting for more than half of all Web pages.[2][3][4] The Internet Mail Consortium (IMC) recommends that all e-mail programs be able to display and create mail using UTF-8.[5] UTF-8 is also increasingly being used as the default character encoding in operating systems, programming languages, APIs, and software applications.[citation needed]