Sometimes I come across websites where the Thai script is seriously mangled. They source claims they are UTF-8, but they're clearly not. They also don't seem to be TIS-620 since if I select that encoding in the browser I still get gibberish.

Can anyone explain what's going wrong (and preferably how to fix)?

Some sites that have this problem:

http://www.sansiri.com/townhouse/Townplus_Onnut/th/sitemap/index.aspx

http://www.tei.or.th/tai/070122.html

http://www.rutningimbel.com/eng/rutnin.php?cmsid=136&language=1

http://www.maethaneedolresort.com/en/promotion.php

http://www.spr.ac.th/krukoy/

Thanks.

Dont know how to fix it but can confirm its not just you..maybe the original text was mangled by the web server.

http://www.spr.ac.th/krukoy/ :

this site falsely claims to be Tis-620 (see page properties or source text).

EDIT: or "windows-874" (Windows codepage 874).

Falsely: if I explicitely change the coding in the browser settings to Unicode it looks plausible.

Doesn't it?

http://www.maethaneedolresort.com/en/promotion.php

This one claims to be "charset=windows-874" (Windows codepage 874).

Worst practice, antiquated

To find out whether I can make it look Ok, I have to change a global windows setting and reboot.

I will try,..

More to come...

http://www.maethaneedolresort.com/en/promotion.php

This page still has issues.

I see Euro-Symbols (you might see something different).

Simply bad website programming.

http://www.rutningimbel.com/eng/rutnin.php?cmsid=136&language=1

A mess!

Seems like some content looks OK with Unicode setting, while the outer frame needs Thai (codepage 874).

I give up here.

Its nothing more than a lot of abysmal web programming.

if I change character encoding in firefox to Unicode it looks ( mostly ) correct in both those pages.

Mostly yes.

But for example in this Lasik center site you then see garbage at the bottom of the page

And the title in the browser tab is always faulty.